Title: Focusing aid for camera
Abstract: An indication of sharpness of focus is provided to a user to assist in focusing a camera. In one embodiment, the camera is coupled to a personal computer. An algorithm is implemented by the personal computer to determine a sharpness of focus based upon differences between the luminance of adjacent pixels in a selected region of an image produced by the camera. A visual or aural indication of the sharpness of focus is provided to the user to enable the user to focus the camera to the sharpest possible focus. Alternatively, the algorithm can be implemented by a processor within a camera so that a visual or aural indicator on the camera provides the indication of sharpness of focus as a user adjusts the focus of the camera.
Patent Number: 6,937,284 Issued on 08/30/2005 to Singh, et al.
| Inventors:
|
Singh; Harjit (Redmond, WA);
Kilzer; Robert T. (Issaquah, WA)
|
| Assignee:
|
Microsoft Corporation (Redmond, WA)
|
| Appl. No.:
|
813520 |
| Filed:
|
March 20, 2001 |
| Current U.S. Class: |
348/346; 348/349 |
| Intern'l Class: |
H04N 005/23.2 |
| Field of Search: |
348/20799,207.1,207.11,345,346,349,354,356,220.1,254,350
396/72
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Ho; Tuan
Attorney, Agent or Firm: Anderson; Ronald M.
Claims
1. A method for assisting a user to manually focus a camera, comprising the steps of:
(a) processing image data produced by the camera to produce a sharpness value
that is indicative of a sharpness of focus of the camera in at least a portion
of an image, the image data comprising a luminance value for each of a plurality
of pixels comprising the image, and the sharpness value being determined based
on differences in luminance between the plurality of pixels comprising the image;
(b) enabling the user to manually focus the camera; and
(c) providing an indication of the focus of the camera to the user as the user
manually focuses the camera, to enable the user to adjust the focus of the camera
to selectively achieve the sharpest focus possible.
2. The method of claim 1, wherein said step of processing comprises the steps of:
(a) determining a luminance value for pixels disposed in at least said portion
of the image;
(b) comparing the luminance value of adjacent pixels disposed in at least said
portion of the image to determine the differences in their luminance values; and
(c) determining the sharpness value as a function of the differences in the luminance
values of adjacent pixels in at least said portion of the image.
3. The method of claim 2, wherein the step of determining the sharpness value
comprises the step of determining a running total of the differences between the
luminance values of adjacent pixels in both a horizontal and a vertical direction.
4. The method of claim 2, wherein at least said portion of the image comprises
at least one of a central portion of the image and side portions of the image.
5. The method of claim 4, further comprising the step of weighting the luminance
values in selected regions of the image included within at least said portion of
the image when determining the sharpness value.
6. The method of claim 1, wherein the step of providing an indication comprises
the step of displaying a visual indicator corresponding to the sharpness value
so that the focus of the camera is visually perceived by the user viewing the visual indicator.
7. The method of claim 6, wherein the step of displaying a visual indicator comprises
the step of displaying a graphical indicator of the sharpness value.
8. The method of claim 7, wherein in the step of displaying a visual indicator
further comprises the step of indicating a maximum of the sharpness value on the
graphical indicator so that as the user adjusts the focus of the camera past a
point of sharpest focus, the user is enabled to reverse the adjustment of the focus
back to the point of sharpest focus corresponding to the maximum of the sharpness value.
9. The method of claim 1, wherein the step of providing an indication comprises
the step of producing an audible sound indicative of the user achieving the sharpest
focus as the user focuses the camera.
10. The method of claim 1, further comprising the step of enabling the user to
link the camera in data communication with a host computing device so that the
step of digitally processing the image data is carried out by the host computing device.
11. The method of claim 1, wherein the step of processing the image data is carried
out by a logic device included within the camera; and wherein the step of providing
an indication uses at least one of an audible indication and a visual indication.
12. The method of claim 11, wherein the audible indication comprises a sound
having a varying audible frequency indicative of the sharpness value.
13. The method of claim 11, wherein the visual indication comprises at least
one of a light having a varying color indicative of the sharpness value, and a
digital display of a number indicative of the sharpness value.
14. The method of claim 1, wherein the step of processing the image data includes
the step of determining a weighted average of luminance for different regions of
the image.
15. A memory medium on which machine readable instructions are stored, said machine
readable instructions, when implemented by a processor, causing steps (a) and (c)
in claim 1 to be carried out.
16. A method for assisting a user to focus a camera that is coupled to a host
computing device on which an image produced using image data from the camera is
displayed, said method comprising the steps of:
(a) digitally processing the image data from the camera using the host computing
device, to determine a sharpness value indicative of a focus of the camera, wherein
the image data that are processed comprise a luminance value for each of a plurality
of pixels comprising the image, and the sharpness value being determined based
on differences in luminance between the plurality of pixels comprising the image;
(b) in response to changes in the focus caused by the user adjusting the focus
of the camera, again determining the sharpness value by digitally processing the
image data; and
(c) indicating the sharpness of focus of the camera to the user as a function
of the sharpness value.
17. The method of claim 16, wherein said step of digitally processing comprises
the steps of:
(a) determining a luminance value for pixels comprising the image;
(b) comparing the luminance value of pixels that are adjacent to each other to
determine the differences in the luminance values; and
(c) determining the sharpness value as a function of the differences in the luminance values.
18. The method of claim 17, wherein the pixels are disposed in one or more predetermined
regions of the image.
19. The method of claim 17, wherein the step of digitally processing further
comprises the step of determining a running total of the differences in at least
one of a horizontal and a vertical direction.
20. The method of claim 17, wherein the step of digitally processing further
comprises the step of weighting the difference in the luminance for pixels in at
least one predefined portion of the image, when determining the sharpness value.
21. The method of claim 16, wherein the step of indicating comprises the step
of providing at least one of a visual and an aural indication of the sharpness
value as the user adjusts the focus of the camera.
22. The method of claim 21, wherein the step of providing the visual indication
includes the steps of:
(a) displaying a graphical indication of the sharpness value; and
(b) displaying an indication of a maximum of the sharpness value that is achieved
as a result of the user adjusting the focus of the camera, so that having adjusted
the focus past a sharpest possible focus corresponding to the maximum, the user
can readily adjust the focus back to the sharpest possible focus indicated by the
maximum that was previously achieved.
23. A system that provides an indication of sharpness of focus to assist a user
in focusing an image, comprising:
(a) a camera that includes a lens having a manually adjustable focus control,
said camera including a light sensor that produces image data in response to light
passing through the lens;
(b) a logic device coupled to receive the image data from the light sensor;
(c) an indicator, coupled to the logic device, said indicator being adapted to
provide an indication of a sharpness of focus of the lens; and
(d) said logic device being configured to implement a plurality of functions, including:
(i) determining a luminance value for each of a plurality of pixels comprising
the image data, and the sharpness value, based on differences in luminance between
the plurality of pixels comprising the image;
(ii) processing the luminance values determined for the image data to determine
a sharpness value indicative of a focus of the lens; and
(iii) indicating to a user the focus of the lens with the indicator, as a function
of the sharpness value, so that a user can determine when the lens is sharply focused.
24. The system of claim 23, wherein at least one of the logic device and the
indicator are disposed within the camera.
25. The system of claim 24, wherein the indicator comprises at least one of an
audio indicator and a visual indicator.
26. The system of claim 25, wherein the visual indicator comprises at least one
of a light having a color that is indicative of the sharpness value, and a numeric
indicator that indicate the sharpness value.
27. The system of claim 25, wherein the audio indicator produces an audible sound
having a frequency that is indicative of sharpness value.
28. The system of claim 23, wherein the camera is adapted to couple to a host
computing device in which at least one of the logic device and the indicator are disposed.
29. The system of claim 23, wherein said logic device:
(a) compares the luminance value of pixels that are adjacent to each other to
determine the differences in their luminance values; and
(b) determines the sharpness value as a function of the differences in the luminance values.
30. The system of claim 29, wherein the pixels are disposed in one or more predetermined
regions of the image.
31. The system of claim 29, wherein the processor determines a running total
of the differences in at least one of a horizontal and a vertical direction.
32. The system of claim 29, wherein the logic device weights the difference in
the luminance for pixels in at least one predefined portion of the image, when
determining the sharpness value.
33. A logic device-readable medium having machine instructions, which when executed
by a logic device, cause a plurality of functions to be implemented, including:
(a) processing image data from a camera to produce a sharpness value that is
indicative of a sharpness of focus of a lens of the camera in at least a portion
of an image, wherein the image data that are processed comprise a luminance value
for each of a plurality of pixels comprising the image, and wherein the sharpness
value is determined based on differences in luminance between a plurality of pixels
comprising the image; and
(b) in response to a user manually focusing a lens of the camera so as to change
the sharpness value, providing an indication of the focus, to enable a user to
selectively improve a sharpness of focus.
34. The logic device-readable medium of claim 33, wherein said machine instructions
cause the logic device to:
(a) determine a luminance value for pixels disposed in at least said portion
of the image;
(b) compare the luminance value of adjacent pixels disposed in at least said
portion of the image to determine the differences in their luminance values; and
(c) determine the sharpness value as a function of the differences in the luminance
values of adjacent pixels in at least said portion of the image.
35. The logic device-readable medium of claim 34, wherein said machine instructions
determine the sharpness value by determining a running total of the differences
between the luminance values of adjacent pixels in both a horizontal and a vertical direction.
36. The logic device-readable medium of claim 34, wherein at least said portion
of the image comprises at least one of a central portion of the image and side
portions of the image.
37. The logic device-readable medium of claim 36, wherein the machine instructions
further cause the logic device to weight the luminance values in selected regions
of the image included within at least said portion of the image when determining
the sharpness value.
38. The logic device-readable medium of claim 33, wherein the machine instructions
cause a visual indicator to be displayed and varied as a function of the sharpness
value, so that the a focus of the lens is visually perceived by a user viewing
the visual indicator.
39. The logic device-readable medium of claim 38, wherein the machine instructions
cause a graphical indicator to be displayed to indicate the sharpness value.
40. The logic device-readable medium of claim 38, wherein the machine instructions
further cause the logic device to indicate a maximum of the sharpness value on
the graphical indicator so that as a user adjusts the focus past a point of sharpest
focus, a user is enabled to readily reverse the adjustment of the focus back to
the point of sharpest focus, corresponding to the maximum of the sharpness value.
41. The logic device-readable medium of claim 33, further comprising an audio
transducer coupled to the logic device, wherein the machine instructions cause
the logic device to produce an audible sound indicative of a user achieving the
sharpest focus as a user focuses the lens.
42. The logic device-readable medium of claim 41, wherein the audible sound has
a varying audible frequency indicative of the sharpness value.
43. The logic device-readable medium of claim 33, wherein the indication of focus
comprises at least one of a colored light display, and a numeric display.
44. The logic device-readable medium of claim 33, wherein the machine instructions
further cause the logic device to determine a weighted average of luminance for
different regions of the image and to provide the indication of sharpness of focus
as a function of the weighted average.
Description
FIELD OF THE INVENTION
The present invention generally relates to a method and system for determining
when a camera is properly focused, and more specifically, to assisting a user to
manually adjust the focus of a camera by providing an indication of the sharpness
of focus of the camera.
BACKGROUND OF THE INVENTION
Broadband access to the Internet has greatly increased the demand for digital
video cameras designed for use with a personal computer (PC). These video cameras,
which are also known as Webcams, are connected to a PC and used to produce compressed
streaming video data for transmission over the Internet, local area, and/or wide
area networks. While early cameras of this type were only capable of producing
black and white images, the development of low cost transistor-based, i.e., complementary
metal oxide semiconductor (CMOS), imaging sensors has enabled reasonably good color
images to be produced by PC cameras, although typically at less than full motion
frame rates (i.e., less than 30 frames/second). However, to minimize costs, such
cameras have relatively few automated controls. For example, they do not include
automatic focusing systems like those normally provided on analog or digital video
cameras intended for general purpose use in recording images on magnetic tape.
On PC cameras, the lens is typically manually adjustable.
Several factors cause the manual focusing of a PC camera to be very frustrating.
Unlike more expensive analog or digital cameras for recording images on tape, PC
cameras typically do not include a viewfinder. If a viewfinder is provided, the
image seen through the viewfinder is not indicative of the lens focus. Instead,
the image produced by a camera must be viewed on a PC monitor. Focusing of the
lens is normally done in a preview mode. Since the image in preview mode is usually
compressed, details that enable the sharpest focus to be visually determined will
be less evident than in an uncompressed image. Also, there is inherently a time
delay between the point at which an image signal is supplied by a PC camera and
the time at which the image is displayed on a monitor. The delay hinders the manual
focusing process. A user manually adjusting the focus on a PC camera while viewing
the preview image produced by the camera on the monitor may believe that the camera
is properly focused, only to watch the image become less sharply focused. The user
will have adjusted the focus control past the point of sharpest focus. The time
delay between an adjustment and the corresponding effect on the sharpness of the
previewed image during the manual focusing process thus makes it difficult to adjust
the camera to achieve the sharpest possible image.
Several other factors contribute to the difficulty in focusing a PC camera.
Typically, the size of the preview image being viewed on a computer monitor while
adjusting the focus is so small that details of the image that might assist in
focusing the camera are not evident. Ambient lighting conditions can also adversely
impact the user's ability to properly focus a camera. For example, a poorly lighted
scene will result in an image with little contrast, causing the sharpness of the
focus to be difficult to visually determine. Sunlight or other lighting conditions
that cause glare on the computer monitor on which the preview image is being viewed
can also interfere with the focus adjustment.
Accordingly, it will be apparent that providing a less subjective indication
of focus sharpness would greatly assist a user in manually focusing a PC camera.
Although conventional through-the-lens focusing systems and automated focusing
features might be provided on a PC camera, the components required for these solutions
to the problem are too expensive to implement at the desired price levels of PC
cameras. There is thus a clear need for a lower cost solution to this problem.
SUMMARY OF THE INVENTION
In accord with the present invention, a method is defined for assisting a user
to manually focus a camera. The method includes the step of digitally processing
image data produced by the camera to produce a "sharpness value" corresponding
to the sharpness of focus of the camera in at least a portion of an image. As the
user manually focuses the camera, an indication of the sharpness of focus achieved
is then provided to the user as a function of this value, to enable the user to
more objectively adjust the focus of the camera.
In a preferred embodiment, the image data preferably comprises a luminance value
for each of a plurality of pixels comprising the image. In this case, the step
of digitally processing includes the step of determining a luminance value for
pixels disposed in at least the portion of the image in which the sharpness of
focus is to be evaluated. Differences in the luminance values of adjacent pixels
disposed in this portion of the image are computed, and the sharpness value is
then determined as a function of these differences.
Also, the step of determining the sharpness value preferably includes the step
of determining a running total of the differences between the luminance values
of adjacent pixels in both a horizontal and a vertical direction. While in most
cases the portion of the image used to determine sharpness of focus will be the
central portion of the image, it is also possible to use the entire image, or the
side portions of the image. In addition, the method may optionally include the
step of weighting the luminance values in selected regions of the image when determining
the sharpness value.
In one form of the invention, the step of providing an indication includes the
step of displaying a visual indicator corresponding to the sharpness value so that
during the step of manually focusing the camera, the user can visually perceive
when the sharpest focus is attained by viewing the visual indicator. For example,
the visual indicator may comprise a graphical indicator, such as a bar graph showing
the current sharpness value. When displaying the visual indicator, the method preferably
includes the step of indicating where the sharpness value was at its maximum, which
corresponds to the sharpest focus, to enable the user to adjust the focus the camera
back to the point of sharpest focus. Alternatively (or in addition to the visible
indicator), an audible sound can be provided that is indicative of the current
focus so that the user will know when the sharpest focus is achieved, as the user
focuses the camera. In such an embodiment, the audible indication may comprise
a sound having a varying audible frequency indicative of the sharpness value.
In one form of the present invention, the user connects the camera in data communication
with a host computing device so that the step of digitally processing the image
data is carried out by the host computing device. In another embodiment, the step
of digitally processing the image data is carried out by a processor within the
camera. In this latter embodiment, the visual indication includes at least one
of a light having a varying color indicative of the sharpness value, a digital
display of a number indicative of the sharpness value, a graphical display indicative
of the sharpness value, and a meter that indicates the sharpness value.
Another aspect of the present invention is directed to a memory medium on
which machine readable instructions are stored. When the machine readable instructions
are implemented by a processor, they cause the steps of the method initially discussed
above to be carried out.
Yet another aspect of the present invention is directed to a system that provides
an indication of sharpness of focus to assist a user in manually focusing the lens
of a camera. This system includes a camera with a lens having a manually adjustable
focus control, and a light sensor that produces image data in response to light
passing through the lens. A processor is coupled to the light sensor to receive
the image data from the light sensor, and an indicator, which is coupled to the
processor, provides an indication of a sharpness of focus of the lens. A memory
in which a plurality of machine instructions are stored is also included and is
coupled to the processor. When these machine instructions are executed by the processor,
they cause it to implement a plurality of functions that are generally consistent
with the steps of the method discussed above.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
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 an elevational view of a generally conventional PC (keyboard and pointing
device not shown) that includes a digital camera, which is focused using the present invention;
FIG. 2 is a functional block diagram of a conventional PC system that is suitable
for implementing the present invention;
FIG. 3 is a block diagram illustrating the overall steps implemented in the
present invention to assist a user in focusing a digital camera;
FIG. 4 is a front elevational view of a digital cameral that includes a processor
for implementing the present invention;
FIG. 5 is a rear elevational view of the digital camera of FIG. 4, illustrating
alternative visual indicators that indicate a sharpness of focus to a user;
FIG. 6 is a block diagram of the functional components used in the digital camera
of FIGS. 4 and 5 to implement the present invention;
FIG. 7 is a view of an image through the viewfinder of the digital cameral of
FIGS. 4-6, showing a bar graph indicator of focus sharpness that is displayed to
a user; and
FIGS. 8A-8D illustrate images of a grid obtained from a digital camera and
displayed by a PC, showing changes that occur in the image and an indicator as
the digital camera is focused.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in FIG. 1, an exemplary PC camera
10 includes a relatively compact
housing
12 having a lens
14 disposed on the front surface of the
housing. A focus control knob
16 is also included on the front housing and
an indicator light
18, which typically comprises a light emitting diode
(LED) is provided on the front of the housing and is periodically illuminated to
indicate when PC camera
10 is actively capturing images through lens
14.
Other types of cameras are focused by rotating a bezel (not shown) around lens
14, or by rotating the lens itself to change its focal point. PC camera
10 is specifically designed for use with a host computing device such as
a PC
20 as shown in FIG. 1.
While it is possible that PC camera
10 can be used with other types
of host computing devices, it will most likely to be used with a PC, such as PC
20 as shown in this Figure. A lead
19 is used to couple PC camera
10 to an appropriate input port, such as a universal serial bus (USB) port.
Alternatively, other input/output (I/O) ports on the computer can be used, depending
upon the format of the signal provided by PC camera
10. While it can be
placed in other locations, PC camera
10 is frequently positioned atop a
monitor
47. The video images that the PC camera produces are displayable
on monitor
47 using appropriate software executed by PC
20. This
software can be transferred from a floppy disk drive
28, a compact disk-read
only memory (CD-ROM) drive
30, or other memory media, or conveyed through
an Internet connection to PC
20 for storage on a hard drive
27. Appropriate
software programs that facilitate the use of a typical PC camera are typically
included with the camera when it is purchased. The software programs facilitate
the use of the PC camera in producing still images and video clips and enable a
user to preview images on monitor
47. By viewing the preview image, the
user can direct the camera at the desired subject so that the subject is framed
properly and, more importantly, the user can focus lens
14 so that the images
produced by PC camera
10 are as sharp as possible.
In the configuration illustrated, PC camera
10 will typically be used
to
produce video clips for transmission by PC
20 over the Internet or other
network, for viewing on the monitors of other PCs that are coupled to the network.
Video clips produced by the PC camera can also be attached to emails that are transmitted
over the Internet or other networks. The software that facilitates the use of the
video clips produced by PC camera
10 will normally provide a compressed
preview image that is displayed on monitor
47. One of several different
compression schemes is typically employed in producing the preview image. A user
will typically be able to choose a compression scheme and a compression ratio to
be applied to the image transmitted over the Internet or other network. Since the
amount of video data produced by PC camera
10 in just a few seconds can
be quite large, it would be somewhat unusual for a user to transmit uncompressed
data over a network. The compression schemes that are used are currently of the
lossy type, e.g., the Joint Photographic Experts Group (JPEG) compression algorithm.
With this and other related lossy type compression algorithms, the quality of the
image is reduced as more compression is applied to a video image. Accordingly,
since the preview image is generally compressed, the present invention substantially
enhances the user's ability to focus lens
14, as explained below.
Exemplary Operating Environment
FIG. 2 and the following discussion are intended to provide a brief, general
description of a suitable computing environment in which the image processing of
the present invention may be implemented. Although not required, the present invention
will be described in the general context of computer-executable instructions, such
as program modules that are executed by a host computing device configured as a
PC. It must be emphasized, however, that the present invention is usable on other
types of computing devices. Generally, program modules include routines, programs,
objects, components, data structures, etc. that perform particular tasks or implement
particular abstract data types. The present invention will preferably be practiced
in a single host computing device, with one or more processors that process multiple
tasks. In a distributed computing environment, program modules may be located in
both local and remote memory storage devices.
With reference to FIG. 2, an exemplary system for implementing the present invention
includes a general purpose computing device in the form of conventional PC
20,
which is provided with a processing unit
21, a system memory
22,
and a system bus
23. The system bus couples various system components, including
the system memory, to processing unit
21 and may be any of several types
of bus structures, including a memory bus or memory controller, a peripheral bus,
and a local bus using any of a variety of known bus architectures. The system memory
includes read only memory (ROM)
24 and random access memory (RAM)
25.
A basic input/output system (BIOS)
26, containing the basic routines that
are employed when transferring information between elements within PC
20
and during start up, is stored in ROM
24. As noted above, PC
20 includes
hard disk drive
27, for reading from and writing to a hard disk (not shown),
magnetic floppy disk drive
28 for reading from or writing to a removable
magnetic disk
29, and CD-ROM drive
30 or other optical disk drive
for reading from or writing to a removable optical disk
31, such as a CD-ROM,
DVD or other optical media. Hard disk drive
27, magnetic disk drive
28,
and optical disk drive
30 are connected to system bus
23 by a hard
disk drive interface
32, a magnetic disk drive interface
33, and
an optical disk drive interface
34, respectively. The drives and their associated
computer-readable media provide nonvolatile storage of computer-readable machine
instructions, data structures, program modules, and other data for PC
20.
Although the exemplary environment described herein employs a hard disk, removable
magnetic disk
29, and removable optical disk
31, it will be appreciated
by those skilled in the art that other types of computer-readable media, which
can store data that is accessible by a computer, such as magnetic cassettes, flash
memory cards, digital video disks, Bernoulli cartridges, RAMs, ROMs, and the like,
may also be used in the exemplary operating environment.
A number of program modules may be stored on the hard disk, magnetic disk
29,
optical disk
31, ROM
24, or RAM
25, including an operating
system
35, one or more application programs
36 (such as a browser
program-if not part of the operating system), other program modules
37,
and program data
38. A user may enter commands and information into PC
20
through input devices such as a keyboard
40 and a pointing device
42.
Other input devices (not shown) may include a microphone, joystick, game pad, satellite
dish, scanner, camera, or the like. These and other input devices are often connected
to processing unit
21 through an input/output (I/O) device interface
46
that is coupled to the system bus and includes serial and parallel ports, as well
as USB ports. Output devices, such as a printer (not shown), may also be connected
to processing unit
21 through I/O device interface
46 that is coupled
to the system bus. Similarly, monitor
47 or other type of display device
is also connected to system bus
23 via an appropriate interface, such as
a video adapter
48, and is usable to display Web pages and/or other information.
In addition to the monitor, PCs may be coupled to other peripheral output devices
(not shown), such as speakers (through a sound card or other audio interface-not shown).
PC
20 preferably operates in a networked environment using logical connections
to one or more additional computing devices, such as to a remote computer
49
that is yet another PC (or alternatively, a server or a mainframe computer) that
typically includes many or all of the elements described above in connection with
PC
20, although only an external memory storage device
50 has been
illustrated in FIG. 2. The logical connections depicted in FIG. 1 include a local
area network (LAN)
51 and a wide area network (WAN)
52. Such networking
environments are common in offices, enterprise-wide computer networks, and intranets.
Preferably, LAN
51 is a back-end subnet connecting a plurality of resource
nodes of the cluster in communication with each other. Preferably, WAN
52
is the Internet.
PC
20 is connected to LAN
51 through a network interface or adapter
53, and to WAN
52 though a network interface or adapter
54.
Network interface
54 may be a router, a modem, a cable mode, a digital subscriber
line (DSL) interface, or other well-known device for establishing communications
over WAN
52 (i.e., over the Internet). Those skilled in the art will recognize
that network interface
53 and network interface
54 may be internal
or external, and may be the same, or even a single interface device. Network interface
53 and network interface
54 are connected to system bus
23,
or may be coupled to the bus via I/O device interface
46, e.g., through
a serial, USB, or other communications port.
In a networked environment, program modules depicted relative to PC
20,
or portions thereof, may be stored in the remote memory storage device. It will
be appreciated that the network connections shown are exemplary and other techniques
for establishing a communications link between the computers may be used, such
as wireless communications.
Overview of Method for Assisting a User to Focus a Camera
As illustrated in FIG. 3, the steps implemented by the present invention to assist
a user in focusing a camera presume that the camera is provided with a focus control,
as shown in a block
70. Such cameras will include a CCD or other type of
imaging light sensor (not shown) that produces an output signal conveying image
data. In a block
72, the image data are converted to luminance data by assigning
a luminance value to each pixel in the image, based upon the intensity of light
at the pixel. Since, if desired, the present invention can be applied in determining
the sharpness of only a selected portion of the image, the step carried out in
block
72 can optionally be implemented for only that selected portion of
the image for which the sharpness of focus is to be determined or evaluated. More
likely though, this step will convert the image data to luminance data for all
pixels in the image.
An initial prototype of the present invention employed a relatively simplistic
algorithm to determine the sharpness of the image as the focus control is adjusted.
A block
74 in FIG. 3 indicates that appropriate algorithm is employed in
carrying out this function. Details of the simplistic algorithm initially developed
for this purpose are explained below. However, it is emphasized that other more
efficient and more accurate algorithms can likely be developed and alternatively
applied, or that modifications can be made to the algorithm discussed below to
improve its capability in determining the sharpness of focus in one or more selected
regions of an image.
Based upon the output of the algorithm implemented in block
74, a block
76 provides an indication of the current sharpness of focus to the user.
This indication can either be visual or aural (or both). Details of several different
embodiments for indicating the sharpness of focus are discussed below. In response
to the indication provided in block
76, the user adjusts the focus of the
camera, as indicated in a block
78. This manual step changes the focus of
the camera as provided in block
70 until based upon the indication of sharpness
of focus provided in block
76, the user determines that the sharpest possible
or optimal focus has been achieved.
Algorithm for Determining Sharpness of Focus
In the algorithm that was employed in a first reduction to practice of the present
invention, it is assumed that in a specified region, the total differences in luminance
between adjacent pixels of the region will be maximized for the region when the
lens of a camera is most sharply focused. In a blurred image that is not sharply
focused, adjacent pixels in both the horizontal and vertical directions within
the region will have less distinct differences in luminance, since the luminance
of any bright objects or dark objects tends to be smeared over the adjacent pixels
when the lens is poorly focused. However, as the focus is improved, the differences
in luminance between adjacent pixels, particularly along the edges of objects or
the edge of bright areas within an image region will increase, reaching a maximum
when the image in the region is at its sharpest possible focus. Thus, the algorithm
determines the sharpness of focus for an image in this exemplary embodiment of
the present invention based upon a total of the differences in luminance between
adjacent pixels in both the horizontal and vertical directions within a defined
region or regions of the image and provides an indication of this total luminance
value to the user as an indication of the sharpness of focus in the region or regions.
Since, due to the delay in processing the image for a current focus condition,
a user may not know when the sharpest possible or optimal focus has been obtained,
until the focus control has been turned past that state, the indication also includes
a maximum indicator. As the user adjusts the focus, the indication of sharpness
of focus will increase as the sharpness improves, and will eventually reach a maximum.
As the user continues to adjust the focus control in the same direction, the indication
of sharpness of focus will decrease below this maximum. However, since the maximum
that was achieved is indicated to the user, it is possible for the user to readily
reverse the direction in which the focus control was adjusted, and return the adjustment
of the control to achieve the maximum that was previously noted.
In the following exemplary lines of software code, the total luminance in a central
portion of a 640×480 pixel image is determined. The central portion is 160×120
pixels in size and in this example, is the region in which the sharpness of focus
is evaluated. The region is identified in the following code by the parameters
EvalWidth for the width of the central region and EvalHeight for the height of
the central region. It should be noted that the software code can be readily changed
to include other regions beside the central region or to include regions around
the periphery of the image, in addition to the central region. One improvement
that is contemplated is the use of different weighting factors for the regions.
Relatively inexpensive cameras have lenses that provide a sharp focus around the
periphery of the image at one setting of the focus adjustment, and provide a sharp
focus in the central portion of the image at a slightly different focus adjustment.
For such cameras, it may be preferable to apply an appropriate weighting to the
total of the differences in luminance for adjacent pixels determined for the central
portion of the image and a different weighting to the total determined in peripheral
regions of the image so that an optimum focus is achieved under the condition in
which neither the total for the peripheral region, nor the total for the central
region is at a maximum value. In most cases, preference (i.e., a greater weighting
factor) will be given to sharpness of focus in the central region, since subjects
of interest an image are typically disposed closer to the central portion of the
image. The exemplary software code that only considers the central portion of the
image is as follows.
- //Image luminance is stored in array ImageLuminance
- ImageWidth=640;
- ImageHeight=480;
- EvalWidth=160;
- EvalHeight=120;
- EvalXOffset=ImageWidth/2-EvalWidth/2; //this is true for a evaluation
region in the middle of the image
- EvalYOffset=ImageHeight/2-EvalHeigh/2; //this is true for a evaluation
region in the middle of the image
- Sharpness=0;
- //compute horizontal sharpness
- for (y=EvalYOffset; y
- for (x=EvalXOffset; x
- Sharpness+=abs(ImageLuminance[y][x]-ImageLuminance[y][x+1]);
//compute vertical sharpness
for (x=EvalXOffset, x
for (y=EvalYOffset; y
Sharpness+=abs(ImageLuminance[y][x]-ImageLuminance[y+1][x]).
FIGS. 8A-8D illustrate an example in which the above algorithm is implemented
to assist in focusing an image of a grid, based upon the sharpness of focus in
the central portion of the image. In this example, an image
130 displayed
on a computer monitor is produced from the image data signal supplied by the PC
camera. Image
130 changes as illustrated in FIGS. 8A-8D, as the user adjusts
the focus of the PC camera. Only a central region
132 is used in determining
the sharpness of focus in this example. In FIG. 8A, it is apparent that image
130
is relatively blurred, since the camera lens is not properly focused. A visual
indication of focus in the form of a bar graph
134 is included with image
130. A maximum sharpness of focus indication
136 is included in the
bar graph, and changes as the focus is improved and a greater maximum sharpness
value is computed. In FIG. 8B, the user has adjusted the focus of the camera, substantially
improving the sharpness of focus in image
130 compared to that shown in
FIG. 8A. A more objective indication of the improvement is apparent from the greater
height of bar graph
134 and the increased value of maximum indication
136.
As the user continues to rotate the focus control in the same direction, a still
more improved focus is obtained for image
130 as shown in FIG. 8C. This
improvement is evident both in the appearance of image
130 in this Figure,
since both the circular and radial lines in the image are now relatively sharply
focused, and in the substantially greater height of bar graph
134 and substantially
greater value of maximum indication
136.
Finally, in FIG. 8D, as the user continues to rotate the focus adjustment
in the same direction, the sharpness of focus of image
130 deteriorates.
This reduced sharpness of focus is evident in the blurring of the circular and
radial lines in image
130 in FIG. 8D and in the reduced height of the bar
graph
134. However, while a reduction in the height of bar graph
134
has occurred in FIG. 8D compared to FIG. 8C, maximum indication
136 remains
at its previous highest value, alerting the user that the direction in which the
adjustment was last turned should be reversed, to achieve the sharper focus shown
in FIG. 8C. Since maximum indication
136 is provided on the bar graph, the
user can readily make fine tuning adjustments to the focus control until bar graph
134 is again equal in height to the maximum indication of FIG. 8C, which
corresponds to the sharpest possible focus.
Camera Implemented Embodiment
From the preceding discussion of FIGS. 8A-8D, it will be apparent that a visual
indication provided on monitor
47 of PC
20 was employed to assist
the user in achieving the sharpest possible focus of PC camera
10 (shown
in FIG. 1). The algorithm used to determine the sharpness of focus is in this case
carried out as PC
20 executes corresponding software instructions stored
in memory, which also cause the PC to display bar graph
134 and maximum
indication
136. However, it is also contemplated that this or other appropriate
algorithm used to determine the sharpness of focus can instead be implemented by
a processor included within a camera and that a visual or aural indication of the
sharpness of focus can be provided to a user of the camera without need for an
algorithm to executed by a host computing device. In this case, the camera can
be used in a standalone mode, without being coupled to a PC or other host computing
device, or even if so coupled, need not require that the algorithm be executed
by the PC or other host computing device.
FIGS. 4-7 illustrate a camera
10′ that has the ability to determine
the sharpness of focus of an image as a user manually adjusts the focus of the
camera. As shown in FIG. 4, camera
10′ includes a housing
80,
a lens
82 coupled to the front of the housing, and a focus bezel ring
84
for adjusting the focus of lens
82. As focus bezel ring
84 is rotated,
the focus of lens
82 is manually adjusted by a user, typically with the
goal being to achieve an optimal focus or the sharpest possible focus of an image
produced by the camera. Camera
10′ includes a battery pack
88
on the base of housing
80 that supplies the electrical energy required by
the camera, enabling it to be decoupled from a PC or other host computing device
to which it may optionally be coupled to transfer a video clip or still images.
While not shown, it is contemplated that a control will be provided for selectively
determining whether the camera captures individual frames or video clips when a
release button
90 is depressed. Camera
10′ also optionally
includes a viewfinder
86 (not coupled to the lens) to assist the user in
framing an image that is to be captured as a single frame or video clip by the camera.
As shown in FIG. 5, the back surface of camera
10′ includes one
of at least three different indicators of the relative sharpness of the image being
viewed by the camera. A digital indicator
94 provides a digital indication
of the relative sharpness of focus of the image and this indication changes as
the user manually adjusts the focus of the camera. If the user continues to adjust
the focus past the point of sharpest focus, a decrease in the value will be evident,
so that the user can reverse the direction of adjustment to return to the maximum
value that was achieved. It is also contemplated that the digital value can begin
alternately displaying the current value and the maximum value that was previously
achieved during the focusing operation.
An alternative visual indication is provided by an analog meter
96, which
includes a needle
98 that changes position as the user adjusts the focus
of the camera. As the sharpness of focus improves, needle
98 moves further
toward the right side of the scale, but as the user passes the point of sharpest
focus, needle
98 will begin moving toward the left, indicating that the
user has passed through the point of sharpest possible focus. By observing the
relative position of needle
98, the user can thus adjust the focus to achieve
the sharpest possible or optimal focus condition.
Yet another visual focus indicator is indicated by a plurality of LEDs
100,
which may be of different color to indicate a relative condition of focus. For
example, the right-most LED can be a yellow color, while the left-most LED is a
red color. The other LEDs will be shades of orange between these two colors. As
the user adjusts the focus of the camera, the LED that is lighted will shift toward
the right, indicating an improved sharpness of focus. While only five LEDs
100
are indicated, it is also contemplated that substantially more LEDs can be used,
or that a LED-type bar graph can be employed, operating generally like the bar
graph described above in connection with PC camera
10.
FIG. 7 illustrates how a bar graph
120 can be included within an image
field
124 of viewfinder
86. Bar graph
120 includes a maximum
indication
122 that is positioned to indicate the maximum sharpness thus
achieved while adjusting the focus of camera
10′. Bar graph
120
can be implemented as a liquid crystal display (LCD) within viewfinder
86,
or as a separate LCD screen that displays image field
124.
In addition to or as an alternative to any of the visual indications of the sharpness
of focus described above, the present invention can optionally include an aural
indication of the sharpness of focus produced with a sonic transducer
92,
which is disposed on the back of camera
10′. An audible signal is
produced by sonic transducer
92 as the user manually adjusts the focus of
camera
10′. As the sharpness of focus is improved, the frequency
of the signal increases, while a reduction in the sharpness of focus causes the
audible signal to decrease in frequency. Alternatively, the sharpness of focus
could be indicated by amplitude or by other audible characteristics of the sound
produced by sonic transducer
92. By simply listening to the audible tone
produced by sonic transducer
92, the user can thus audibly determine when
the sharpest possible or optimal focus of the camera has been achieved.
Further details of the functional components employed within camera
10′
are illustrated in FIG. 6. As shown therein, the light passing through manually
focused lens
82 is incident on a CCD array
114 that produces the
image data signal. The image data signal is applied to an A-D converter and interface
116, which converts the analog signal to digital luminance values for each
pixel in at least a selected region of interest in which the sharpness of focus
is to be monitored. The luminance data in digital form are provided to a central
processing unit (CPU)
110. Machine instructions and other data are stored
in a memory
112 that includes both ROM and RAM. These machine instructions
cause CPU
110 to implement the algorithm described above or some other appropriate
algorithm to determine the sharpness of focus. Based upon the relative sharpness
value determined by implementing the algorithm, CPU
110 drives an indicator
118, which is either visual, aural, or both. Electrical current for CPU
110 and each of the other components in camera
10′ is provided
by battery pack and power supply
88.
Although the present invention has been described in connection with the
preferred form of practicing it, those of ordinary skill in the art will understand
that many modifications can be made thereto within the scope of the claims that
follow. Accordingly, it is not intended that the scope of the invention in any
way be limited by the above description, but instead be determined entirely by
reference to the claims that follow.
*
