Digital Camera Patent Abstract
A shutterless digital camera includes an optical viewfinder having
a pair of spaced apart mirrors for facilitating in one mode of operation
through-the-lens viewing of an object image to be captured and for
facilitating in the same one mode of operation through-the-lens
display unit viewing of a captured object image. A mirror control
system facilitates the moving of at least one of the mirrors to
permit the object image to be captured and further facilitates the
moving of at least the other one of the mirrors to permit display
unit viewing of the captured object image. The method of using the
shutterless digital camera includes passing object light indicative
of the object image through a primary lens system and a secondary
lens system to permit a user to view the object image prior to the
object image being stored for reproduction purposes and subsequently
passing display light indicative of the object image through the
secondary lens system only to permit the user to view the object
image subsequent to the object image being stored for reproduction
purposes. Digital Camera Patent Claims
We claim:
1. An optical viewfinder for facilitating the viewing of an object
image in a digital camera, comprising, a pair of spaced apart mirrors,
wherein one mirror is partially reflective and partially transmissive
for facilitating in one mode of operation through-the-lens viewing
of the object image to be captured and for facilitating in said
one mode of operation an auto exposure adjustment for an image sensor
and subsequently following said auto exposure adjustment through-the-lens
display unit viewing of a captured object image; and a mirror control
system for facilitating the moving of only the partially reflective
and partially transmissive mirror for said auto exposure adjustment
and for facilitating the moving of only the other mirror to permit
the display unit viewing of the captured object image.
2. An optical viewfinder for facilitating the viewing of an object
image in a digital camera, comprising: a pair of spaced apart mirrors
for facilitating in one mode of operation through-the-lens viewing
of the object image to be captured and for facilitating in said
one mode of operation through-the-lens display unit viewing of a
captured object image; and a mirror control system for facilitating
the moving of at least one of the mirrors to permit the object image
to be captured and for facilitating the moving of at least the other
one of the mirrors to permit the display unit viewing of the captured
object image; and wherein one of said pair of spaced apart mirrors
is about twenty percent transmissive and about eighty percent reflective.
3. An optical viewfinder according to claim 2, wherein said mirror
control system causes said pair of spaced apart mirrors to move
in unison with one another.
4. An optical viewfinder according to claim 2, wherein said mirror
control system causes said pair of spaced apart mirrors to move
independently of one another.
5. An optical viewfinder according to claim 2, wherein an individual
one of said pair of spaced apart mirrors is partially transmissive
and partially reflective.
6. A digital camera, comprising: a primary lens system including
a fixed primary lens and at least one moveable focusing lens for
focusing an object image to be captured as a still digital image
at a desired location; a secondary lens system including an adjustable
diopter for facilitating the focusing of said object image relative
to the vision of a user of the digital camera; an optical viewfinder
system for through-the-primary lens system viewing of said object
image to be captured and for through-the-secondary lens system viewing
of a captured object image; said optical viewfinder system including
a pair of spaced apart mirrors for helping to define a primary light
path between said primary lens system and said secondary lens system
to facilitate in one mode of operation the through-the-primary lens
viewing of the object image to be captured and to further facilitate
in said one mode of operation the through-the-secondary lens viewing
of the captured object image, and a micro display unit for further
facilitating the through-the-secondary lens viewing of the captured
object image; and an imaging system disposed at least partially
in a secondary light path and coupled to said micro display for
capturing the object image and for supplying said micro display
with an electrical signal indicative of the object image during
said one mode of operation for further facilitating the through-the-secondary
lens viewing of the captured object image; and wherein one mirror
is partially reflective and partially transmissive for facilitating
in said one mode of operation an auto exposure adjustment and subsequently
following said auto exposure adjustment through-the-secondary-lens
display unit viewing of a captured object image; and a mirror control
system for facilitating the moving of only the partially reflective
and partially transmissive mirror for said auto exposure adjustment
and for facilitating the moving of only the other mirror to permit
the display unit viewing of the captured object image.
7. A digital camera according to claim 6, wherein said imaging
system further includes: an image converting device disposed in
said secondary light path for converting light indicative of the
object image to be captured into a signal indicative of the object
image to be captured; and an image storage device responsive to
said signal for storing information indicative of the captured object
image.
8. A shutterless digital camera, comprising: an image sensor coupled
to a display unit to facilitate viewing a captured image; a pivotally
mounted partially reflective, partially transmissive mirror disposed
in a primary light path for preventing over driving said image sensor
and for directing light indicative of an object image along a through-the-lens
light path to facilitate optical viewing of an image to be captured;
and a path selecting mirror mounted in said through-the-lens light
path for independent or simultaneous movement with said partially
reflective, partially transmissive mirror to further facilitate
viewing of said captured image.
9. The shutterless digital camera according to claim 8, further
comprising: a mirror control system for determining whether said
path selecting mirror should be moved independently of or simultaneously
with said partially reflective, partially transmissive mirror.
10. The shutterless digital camera according to claim 9, further
comprising: a housing for supporting therein said image sensor,
said display, said pivotally mounted partially reflective, partially
transmissive mirror and path selecting mirror.
11. The shutterless digital camera according to claim 10, further
comprising: a capture object image switch to facilitate user activation
mirror control system.
12. The shutterless digital camera according to claim 11, wherein
said image sensor, in an auto exposure mode of operation, generates
an ambient light output signal in response to a user depressing
said capture object image switch to a first stop position.
13. The shutterless digital camera according to claim 12, wherein
said mirror control system causes said partially reflective, partially
transmissive mirror to pivot out of said primary light path when
said ambient light output signal does not exceed a given threshold
level; whereby the light indicative of an object image is directly
focuses on said image sensor to facilitate an auto exposure adjustment
under low ambient light conditions.
14. The shutterless digital camera according to claim 13, wherein
said mirror control system causes said partially reflective, partially
transmissive mirror and said path selecting mirror to move in unison
with one another.
15. The shutterless digital camera according to claim 13, wherein
said mirror control system causes said partially reflective, partially
transmissive mirror and said path selecting mirror to move independently
of one another.
16. The shutterless digital camera according to claim 9, wherein
said mirror control system causes said partially reflective, partially
transmissive mirror and said path selecting mirror to move in unison
with one another.
17. The shutterless digital camera according to claim 9, wherein
said mirror control system causes said partially reflective, partially
transmissive mirror and said path selecting mirror to move independently
of one another.
18. The shutterless digital camera according to claim 16, wherein
said partially reflective, partially transmissive mirror is twenty
percent transmissive and eighty percent reflective.
19. The shutterless digital camera according to claim 17, wherein
said partially reflective, partially transmissive mirror is twenty
percent transmissive and eighty percent reflective.
20. A shutterless digital camera, comprising: image sensor means
coupled to a display means to facilitate viewing a captured image;
partially reflective, partially transmissive light means disposed
in a primary light path for preventing over driving said image sensor
means and for directing light indicative of an object image to be
directed along a through-the-lens light path to facilitate optical
viewing of an image to be captured; and light path selecting means
disposed in said through-the-lens light path for independent or
simultaneous movement with said partially reflective, partially
transmissive light means to further facilitate viewing of said captured
image.
21. A digital camera, comprising: image sensor means for receiving
an object image under unknown ambient lighting conditions; movable
light attenuation means disposed between a primary lens system and
said image sensor means; movable light path selecting means disposed
between a secondary lens system and a viewfinder lens; and controller
means for causing said movable light attenuation means and said
movable light path selecting means to move in unison under high
ambient lighting conditions and to move independently under low
ambient lighting conditions.
Digital Camera Patent Description
TECHNICAL FIELD
The present invention relates to a digital photography system and
method of using the system to provide electronic still photographs.
The invention more particularly relates to a shutterless single
lens digital still camera and method of using the camera for forming
electronic still photographs using a single mode operation for both
previewing and reviewing operations.
BACKGROUND OF THE INVENTION
With the advent of small low cost digital storage devices, digital
still cameras are rapidly replacing silver halide film cameras as
the camera of choice. In this regard, such low cost digital storage
devices are enabling digital cameras to provide high resolution
electronic still photographs. Moreover, with the current improvements
in ink jet and laser printer technologies, inks, paper, and image
reproduction processes are allowing color prints to be generated
from captured digital images that are of substantially the same
quality as that provided through silver halide color prints.
While digital still cameras have been replacing silver halide color
print cameras as the preferred choice of the consumer, one of the
biggest drawbacks with most, if not all digital cameras, has been
size. That is, in order for a user to capture and review an electronic
still image such digital devices have incorporated large, bulky
and expensive liquid crystal display units and other light converting
devices, such as charge coupled devices and the like. More particularly,
in order for a user to preview an image to captured, the digital
camera must give feedback to a user of what area of a scene to be
photographed will be captured when a picture is taken. This has
traditionally been accomplished using a built-in device called an
optical viewfinder or optical window that enables the user to visualize
the scene and see exactly what area of the scene that will be captured
by the camera lens system. The ability of providing an accurate
representation of the image to be capture has been implemented in
two different manners between what is known in the state of the
art as a through the lens (TTL) camera and a point and shoot (PAS)
camera.
In the TTL camera, as a user views a scene to be photographed,
he or she utilizes the camera viewfinder. More particularly, the
user is viewing the scene through the lens system of the camera.
That is, with the help of an internally positioned mirror within
the TTL camera, the light passing through the lens system is reflected
by the internal mirror and directed to the optical viewfinder for
consideration by the user. When the user is satisfied with the scene
to be captured, the mirror is repositioned allowing a direct light
path to the photosensitive plane of the camera, and thus, allowing
the scene to be captured as viewed through the optical viewfinder.
The PAS camera is much less expensive and does not allow the user
to view the scene through the primary lens system. Instead, the
optical viewfinder is provided with a secondary lens system that
moves in and out in tandem with the primary lens system. In short
then, in the PAS camera two separate light paths are established;
one light path for the primary lens system to the photosensitive
plane of the camera and another light path through the secondary
lens system to the viewfinder for the scene preview benefit of the
user.
In either implementation whether TTL or PAS, once the user has
captured the image, the user can then only view the captured image
by switching the camera mode of operation from a preview mode of
operation to a review mode of operation. The change in the mode
of operation permits the user to view the previously stored captured
images on a liquid crystal display panel of the camera.
Therefore it would be highly desirable to have a new and improved
digital camera that would permit the user to immediately view a
captured image without switching the mode of camera operation and
without the need of viewing the image on an externally mounted liquid
crystal display device.
SUMMARY OF THE INVENTION
In accordance with the present invention, a shutterless digital
camera includes a low profile digital camera housing sufficiently
small to fit within the shirt or blouse pocket of a user. An optical
viewfinder having a pair of spaced apart mirrors mounted within
the camera housing facilitate in one mode of operation through-the-lens
viewing of an object image to be captured, and in the same one mode
of operation, through-the-lens display unit viewing of a captured
object image. A mirror control system coupled to the spaced apart
mirrors facilitate the moving of at least one of the mirrors to
permit the object image to be captured and further facilitate the
moving of at least the other one of the mirrors after an image has
been captured to permit display unit viewing of the captured object
image.
The method of using the shutterless digital camera includes passing
object light indicative of the object image through a primary lens
system and a secondary lens system to permit a user to view the
object image prior to the object image being stored for reproduction
purposes and subsequently passing display light indicative of the
object image through the secondary lens system only to permit the
user to view the object image subsequent to the object image being
stored for reproduction purposes.
BRIEF DESCRIPTION OF DRAWINGS
The above-mentioned features of this invention and the manner of
attaining them will become apparent, and the invention itself will
be best understood by reference to the following description of
the embodiment of the invention in conjunction with the accompanying
drawings wherein:
FIG. 1 is a pictorial view of a shutterless digital camera which
is constructed in accordance with the present invention;
FIG. 2 is a diagrammatic top plane view of the camera of FIG. 1,
illustrating a through the lens optical path for previewing an image
to be captured;
FIG. 3 is a diagrammatic side plane view of the camera of FIG.
1, illustrating a through the mirror optical path for facilitating
the automatic setting of camera operating conditions;
FIG. 4 is a front plane view of the camera of FIG. 1;
FIG. 5 is another diagrammatic top plane view of the camera of
FIG. 1, illustrating another optical path for facilitating the viewing
of a captured digital image;
FIG. 6 is another diagrammatic side plan view of the camera of
FIG. 1, illustrating another through the lens optical path for capturing
an object image;
FIG. 7 is a block diagram of the operating components of the shutterless
digital camera of FIG. 1; and
FIG. 8 is a high level flow chart illustrating control program
steps for capturing an object image with the camera of FIG. 1.
FIG. 9 is a high level flow chart illustrating control program
steps for automatically setting the focus of the camera of FIG.
1; and
FIG. 10 is a high level flow chart illustrating control program
steps for automatically adjusting the exposure level of the camera
of FIG. 1.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to the drawings, and more particularly to FIG. 1
thereof, there is shown a low-profile, pocket-size shutterless digital
camera 10 which is constructed in accordance with the present invention.
The digital camera 10 is capable of capturing and transmitting desired
ones of a plurality of stored digital still images without the use
of an externally visible display device.
Considering now the digital camera 10 in greater detail with reference
to FIGS. 1-6, the digital camera 10 generally includes a low profile
compact housing 12 that is sufficiently small to fit within a shirt
or blouse pocket of a user (not shown). The housing 12 is generally
rectangular in shape having disposed therein an operating system
compartment 14 and a power supply or battery compartment 16. The
operating system compartment 14 encloses and supports the operative
components of the camera 10 in a conventional manner, while the
battery compartment 16 encloses and supports a pair of rechargeable
batteries 18 and 19 for providing the camera components with the
necessary electrical energy to facilitate normal camera operations.
In order to capture a desired object image or scene, the camera
10 includes a shutterless image capture system 20 and a primary
lens system 22 that is at least partially disposed in a primary
light path 30 within the operating system compartment 14. A micro
processor controlled mirror system 21, as best seen in FIG. 7, directs
light along a plurality of different light paths within the camera
10 to facilitate both image capture, via an image sensor 34 and
image review, via an internally mounted micro display 44 during
the same camera operation as will be explained hereinafter in greater
detail.
As best seen in FIG. 3, the primary lens system 22 includes a primary
lens 24 mounted at about a forward sidewall of the housing 12 and
a pair of internally mounted movable focusing lens 25 and 26 respectively.
The focusing lens 25 and 26 are independently moveable along a portion
of the primary light path 30 to cooperate with the primary lens
24 for helping to automatically focus light reflecting from an object
into the image sensor 34 forming part of the shutterless image capture
system 20. A fixedly mounted mirror 32 disposed in the primary light
path 30 directs light traveling along the primary light path 30
downwardly along an image capture path 40 into the image sensor
34. In the preferred embodiment of the present invention, the image
sensor 34 is a CMOS sensor. It will be understood however, by those
skilled in the art that other types and kinds of image sensors,
such as a charge coupled device, can also be utilized for light
converting purposes.
The shutterless image capture system 20 also includes a microprocessor
36 having coupled thereto the image sensor 34, and a high density
storage device 38. The micro processor 36 under the control of an
image capture algorithm 600 and an automatic focus algorithm 800
control the mirror system 21 and the focusing lens 25 and 26 to
provide a user of the camera 10 with clear sharp optical and digital
images as will be explained hereinafter in greater detail. As mentioned
earlier, the image sensor 34 is preferably in the form of a CMOS
device, for converting light traveling along the image capture path
40 into an electrical signal indicative of the object image.
Considering now the mirror system 21 in greater detail with reference
to FIGS. 2 and 5, the mirror system 21 generally includes a pivotally
mounted partially reflective, partially transmissive mirror 42 that
is mounted in the primary light path 30 between the image sensor
34 and the focusing lens 25 and 26. The mirror 42 attenuates the
light traveling to the image sensor 34 to prevent over driving the
image sensor 34 for image capture purposes but does not sufficiently
attenuate the light traveling to the image sensor 34 to prevent
the automatic adjustment of exposure settings for current ambient
light conditions via an auto exposure subroutine 700. In this regard,
if the ambient light conditions are insufficient to activate the
automatic exposure feature of the camera 10, the microprocessor
36 will cause the mirror 42 to be pivoted out of the primary light
path 30 allowing the light traveling along the image capture path
40 to reach the image sensor 34 without the light being attenuated.
More particularly, the microprocessor 36 under the control of the
automatic exposure algorithm 800 adjusts the exposure settings for
the camera 10 and then, either before or after deflecting the mirror
42 from the primary light path 30 permits the image sensor 34 to
capture the desired object image. In this regard, the camera 10
is a true shutterless camera as the light sensitive sensor 34 is
always receiving light through the primary lens system 22.
The digital camera 10 further comprises an optical viewfinder system
42 (FIG. 7) that includes a micro display 44 and a secondary lens
system 43 for gathering and focusing light emanating from the object
to be captured or from the digital image of the captured object
via the micro display 44. A path selecting mirror 46 forming part
of the mirror system 21, is mounted in a through-the-lens light
path 50 for either independent or simultaneous movement with the
partially reflective partially transmissive mirror 42. In this regard,
the path selecting mirror 46 is mounted within the operating system
compartment 14 in the through-the-lens light path 50 that intercepts
the light traveling along the primary light path 30 after the light
has been deflected into the through-the-lens light path 50 via the
partially reflective partially transmissive mirror 42. The mirrors
42 and 46 operate under the control of the microprocessor 36 to
permit a user to either preview an object image to be captured via
the through-the-lens light path 50 or review a captured object image
via a review light path 60. In short then, the optical viewfinder
system 48 under the control of the microprocessor 36 selectively
permits a user to visualize either an object or scene to be captured
or alternatively, once an object image or scene is captured, to
visualize the captured object or scene through the viewfinder system
48 without the use of an externally visible display device.
In order to permit the user to focus the camera 10 for the eye
of the user relative to previewing and reviewing an object image,
the secondary lens system 43 includes a secondary set of lenses,
indicated generally at 61 and a redirecting mirror 62 for causing
light from the object image or the micro display 44 to be focused
into a housing mounted diopter 64 having a rim adjustor 66. The
rim adjustor 66 rotates under the control of the user to change
or adjusts the focus of the optical viewfinder system 42 so that
either a captured image displayed on the micro display 44 or a through-the-lens
object image being previewed prior to capture appears "in focus"
to the eye of the user.
The camera 10 also includes a strobe flash, indicated generally
at 74, to facilitate illuminating an object image under low ambient
light conditions. The strobe flash 74 responds to a flash on/off
signal coupled from a flash on/off switch 78 forming part of a group
68 of external control switches.
As best seen in FIG. 2, the camera 10 further includes a universal
system bus (USB) or jack 28 that is disposed in a jack compartment
15 located adjacent to the battery compartment 16. The jack compartment
15 is accessible via a jack compartment door 54 that is mounted
to the camera housing 12 by a set of internal hinge members 56 and
58 respectively. The internal hinge members 56 and 58 are disposed
in such a manner to permit the jack compartment door 54 to freely
open without displacing the camera housing 12 from a normally horizontal
plane orientation when the underside or bottom of the camera 10
is resting on a supporting surface.
The digital camera 10 also includes a user interface arrangement
67 that includes the group 68 of external control switches and a
status display unit 72 in the form of a flat panel liquid crystal
display. The group 68 of control switches are coupled to the microprocessor
36 via a switch input/output buffering device 69 (FIG. 7) and input/output
bus indicated generally at 80.
As best seen in FIG. 1, the status display 72, and the group 68
of switches, are housing mounted for easy viewing and manipulation
by a user. In this regard, the user interface arrangement 67 helps
a user to control camera operations in a fast and convenient manner
using a graphical user interface generated by the micro processor
36 and a control program 100 that includes the capture image algorithm
700. The control program 100 as will be explained hereinafter in
greater detail, controls camera operations including power on/off,
menu selections, flash on/off, zoom in, zoom out, scroll forward,
scroll backward and set self time mode. It should be noted that
the status display unit 72 mounted in a top side of the camera 10
for external viewing by the user, permits the user to view alphanumeric
and graphical information only. In this regard, the status display
unit 72 does not display either object images to be captured or
captured object images. Instead the status display unit 72 is only
utilized too provide the user with a visual indication of various
ones of the camera operating conditions, such as for example, a
camera power on/off indication or a flash mode selected indication.
A complete list of the user interface control switches and their
associated functions are provided in Table 1.
TABLE 1 Manually Op- erable Switch Function Power On/ Pushbutton
82 to power camera 10 On and Off. Power Off Capture Object A two-position
pushbutton 84 to capture an object image. Image Scroll Up/ Pushbutton
86 operates to scroll up through a group of Zoom Out captured images
or through a menu selection displayed on the micro display 52 when
the camera 10 is operated in a menu mode. When the camera 10 is
operating in a capture image mode, pushbutton 86 functions as a
zoom out switch, while depressed. Scroll Down/ Pushbutton 88 operates
to scroll down through a group of Zoom In captured images or through
a menu selection displayed on the micro display 52 when the camera
10 is operated in a menu mode. When the camera 10 is operating in
a capture image mode, pushbutton 88 functions as a zoom in switch
while depressed. Strobe Flash Pushbutton 78 to turn a strobe flash
74 to a desired On or On/Off Off mode, an automatic mode, a red
eye AUTO mode, or a red eye On mode, where the mode selected is
displayed on the status display unit 72. Menu/Image Pushbutton 76
to cause the micro display 52 to display Mode menu selections. Image
Mode Pushbutton 75 to display captured images when the cap- ture
object image pushbutton 84 is activated and view preview object
images when the capture object image pushbutton 84 is not activated.
Considering now the operation of the camera 10 in greater detail
with reference to FIGS. 1-6, when a user desires to capture a desired
object or scene as a digital still image, the user activates the
camera 10 by depressing the power on/off pushbutton 82. To verify
that the camera 10 is activated the user views the status display
72 for such a power on indication.
Next the user activates the menu/image mode switch 76 to place
the camera in the image mode of operation. The user may verify this
mode of operation by looking through the diopter 64 to verify through-the-lens
operation. That is, the user will be able to see an object or scene
to be captured through the viewfinder system 48 via the diaopter
64.
The user next points the camera 10 at the object to be captured
and depresses the capture image pushbutton 84 half way or to a first
stop position. The microprocessor 36 responds to the activation
of pushbutton 84 by executing two algorithms: the auto exposure
algorithm 700 and an auto focus algorithm 800, which algorithms
will be described hereinafter in greater detail. At this point,
it will be sufficient to indicate that the execution of the algorithms
700 and 800 cause the exposure and focus of the camera 10 to be
automatically set or adjusted.
Next the user may desire to change the image to be captured by
zooming the camera 10 in or out using the pushbuttons 86 and 88
respectively. In this regard, the user releases the capture object
image switch 84 and activates either pushbutton 86 or pushbutton
88 to acquire a desired image to be captured. When the user is satisfied
with the image to be captured as viewed via the diaopter 64, the
user once again depresses the capture object image switch 84 to
the first stop position permitting the camera 10 to set the focus
and exposure settings for the camera 10. If the user is satisfied
with the image to be captured, the user simply depresses the capture
image pushbutton 84 to its fully depressed or second stop position.
When pushbutton 84 is fully activated, the microprocessor 36 executes
a capture image algorithm 600 that will be described hereinafter
in greater detail. In short however, the algorithm 600 causes the
pivotally mounted mirror 42 to pivot or swing out of the primary
light path 30, permitting light entering through the primary lens
system 22 to be focused onto the image sensor 34. The user is able
to verify the capture operation since the path selection mirror
46 simultaneously swings or pivots blocking the through-the-lens
path 50 and establishing the light path from the diaopter 64 to
the micro display 44 via the review light path 60. In this regard,
the object or scene previously saw by the user switches temporarily
to a black image.
The microprocessor 36 then causes the CMOS image sensor device
34 to convert the light focused from the primary lens system 22
into an electrical signal indicative of the captured object or scene.
Once the image has been captured via the image sensor 34, the micro
processor 36 causes the captured image to be stored in the storage
device 38 in a compressed image format, just as in a JPEG image
format.
When the captured image is stored in the storage device 38, the
microprocessor 36 causes the captured image to be accessed from
the storage device 38 and displayed on the micro display 44. In
this regard, the black image being viewed by the user switches to
the captured image. In short then, the user is able to immediately
view the image captured to determine whether a desired image was
in fact captured. The user then releases the capture object image
pushbutton 84.
Upon releasing the captured image pushbutton 84, the micro processor
36 under control of the capture image algorithm 600, causes the
mirrors 46 and 48 to swing or pivot back to their original positions
once again permitting the user to view an object of scene to be
capture via the through the lens light path 50. The above described
image capture process is then repeated a desired number of times
or until the storage device 38 is full whichever occurs sooner.
Considering now the camera 10 in still greater detail with reference
to FIG. 7, when the user depresses the capture object image switch
84 to the first stop position, the microprocessor 36 under control
of the auto exposure algorithm 700 determines a proper exposure
setting for the image sensor 34. More particularly, when the micro
processor 36 receives an adjust focus signal from the image capture
switch 84 being depressed to the first stop position, the microprocessor
36 during a first sampling period T.sub.1 samples the ambient light
output signal from the image sensor 34. The sampling period T.sub.1
is a short sampling period as there is no need to sample the entire
image to be captured. Instead, the algorithm 700 is only interested
in sampling the intensity of the light entering the camera 10 via
the primary light path 30 and as attenuated by the mirror 42 before
reaching the image sensor 34 via the fixed mirror 32 and image capture
path 40.
The microprocessor 36 responds to the ambient light output signal
from the image sensor 34 by subdividing the signal into a series
of smaller samples that are then arranged in a desired order, such
as a matrix arrangement, strip of contiguous sample areas, or a
set of overlapping sample areas. In this regard, a binary one is
established for a given area if its gray level equals or exceeds
a predetermined luminance level of about N % and a binary zero is
established for a given area if its gray level is less that the
predetermined luminance level of about N %. The number N is between
about 10 and about 30 for most exposures settings. A more preferred
number N is between about 15 and about 25, and the most preferred
number N is about 18. The binary values derived from the individual
image areas or sets of image areas are then utilized to form a pointer
that locates a corresponding exposure setting or level to be applied
to the image sensor 34 of the camera.
If the ambient light output signal from the image sensor 34 does
not exceed a given threshold level, the microprocessor 36 causes
the mirror 42 to pivot out of the primary light path 30 allowing
light entering the primary lens system 22 to be directly focused
on the image sensor 34 without being attenuated. The steps of subdividing,
assigning, and forming are repeated to locate another corresponding
exposure setting or level to be applied to change the gain settings
of the image sensor 34 to achieve a desire exposure level.
Considering now the camera 10 in still greater detail with reference
to FIG. 7, when the user depresses the capture object image switch
84 to the first stop position, the microprocessor 36 under control
of the auto focus algorithm 800 determines a proper focus setting
for the primary lens system 22. More particularly, when the micro
processor 36 receives an adjust focus signal from the image capture
switch 84 being depressed to the first stop position, the microprocessor
36 during a first sampling period T.sub.1 moves the focus lens 26
from an initial hyperfocal position to a full range focusing position.
While the focusing lens 26 is moving, the auto focus algorithm 800
causes the micro processor 36 to capture and temporarily store a
series of output signals from the image sensor 34.
At the end of the sampling period T.sub.1 the micro processor 36
under control of the auto focus algorithm 800 causes the focusing
lens 26 to return to its initial hyperfocal position during another
sampling period T.sub.2. During the sampling period T.sub.2, the
microprocessor 36 under control of the auto focus algorithm 800
determines which one of the captured and stored image signals is
the best focused image. This is accomplished by taking the derivative
of a plurality of lines of pixels in each image, and weighting the
center more heavily than the periphery. The image with the greatest
absolute value of derivative is determined to be the image in the
clearest focus.
If a best focused image is determined during the time period T.sub.2,
the microprocessor 36 under control of the auto focus algorithm
800 causes the focus lens 26 to move to the best focused position
during another time period T.sub.3. If the auto focus algorithm
800 did not determine a best focused position during the time period
T.sub.2, the microprocessor 36 causes the focus lens 26 to remain
in the hyperfocal position.
The auto focus position determined by the auto focus algorithm
800 will remain set in the camera 10 if the user fully activates
the capture object image switch 84 within a predetermined time period
T.sub.4 from the end of time period T.sub.3. Stated otherwise, the
auto focus feature is disabled and the primary lens system remains
set in the last focus position determined by the auto focus algorithm
800.
If the user fails to fully activate the capture object image switch
84 within the predetermined time period T.sub.4 from the end of
time period T.sub.3, the auto focus feature is once again activated
and proceeds as described.
Considering now the viewfinder system 48 in greater detail with
reference to FIGS. 2 and 5, the mirror system 21 includes a support
arm 81 mounted for pivot movement within the housing 12. The support
arm 81 is coupled to a motor 83 forming part of a motor servo system
96 that is responsive to the microprocessor 36. The motor servo
system 96 and more particularly the motor 83 is also coupled the
focusing lens 25 and 26 respectively to facilitate their movement
along the primary light path 30 for image focusing purposes. The
support arm 81 has mounted at its distal end the path selecting
mirror 46. In this regard, when the support arm 81 pivots about
its longitudinal axis, the path selecting mirror 46 is pivotally
moved into the through-the-lens light path 50. When the path selecting
mirror 46 is so positioned, the viewfinder system 48 is blocked
from observing the light traveling along the primary light path
30. The path selecting mirror 46 is also so positioned to permit
the viewfinder system 48 to observe light originating from the micro
display 44.
Considering now the image capture system 20 in greater detail with
reference to FIGS. 2, 5 and 7, the image capture system 20 permits
a user to immediately review a captured image once the image has
been stored in the storage device 38. In this regard, the image
sensor 34 converts light into an electrical signal in the form of
a digital signal output that is buffered to the micro processor
36 from a buffer memory 90 for storage in the storage device 38.
The buffer memory 90 forms part of a light converting system 19
that also includes a timing generator 92 and gain control circuit
94 to help facilitate the auto focus, auto exposure and image capture
features of the camera 10.
The image capture system 20 also includes a pivotally mounted mechanical
linkage 85 that is coupled to the motor 83. The support arm 81 has
mounted at its distal end the partially reflective partially transmissive
mirror 42. In this regard, when the mechanical linkage 85 pivots
from a blocking position to an open position, the mirror 42 is moved
into the through-the-lens light path 50 blocking the viewfinder
system 48 and sufficiently opening the primary light path 30 to
permit light to reach the deflection mirror 32 without being attenuated.
In the preferred mode of operation the mirror 42 and the mirror
46 move simultaneously. However it should be understood by those
skilled in the art that the mirrors 42 and 46 can be moved independently
of one another to accomplish the same result. Thus for example,
under low ambient light conditions when the user depresses the image
capture pushbutton 84 to a half way position, the mirrors 42 and
46 remain stationary while the auto exposure and auto focus algorithms
700 and 800 are executed by the microprocessor 36. In this regard,
if there was insufficient ambient light the capture image routine
600 may delay the moving of the path selecting mirror 46 when the
user fully depresses the pushbutton 84. In this situation, the capture
image routine 600 first causes the mirror 42 to be moved into the
through-the-lens path 50 allowing the auto exposure algorithm 700
to adjust the exposure setting of the camera prior to capturing
the object image. Once the auto exposure subroutine 700 is executed,
the capture image routine 600 proceeds by capturing the image and
moving the path selecting mirror 46 to permit the user, via the
viewfinder system 48, to observe light originating from the micro
display 44. In this example therefore, the mirrors 42 and 46 move
independently of one another and not simultaneously as described
in the preferred embodiment of the present invention.
Considering now the capture image routine 600 in greater detail
with reference to FIG. 8, the capture image routine 600 begins at
a start command 602 that is initiated whenever the user depresses
the image capture switch 84 to a half way position. Upon detection
of the activation of the image capture switch 84, the capture image
routine 600 advances to a decision step 604 to determine whether
the user has depressed the image capture switch 84 to a fully depressed
position within T seconds of the last time the switch 84 was fully
depressed. In this regard, if the switch 84 has not been fully depressed
the routine 600 proceeds to a call command 620 that calls the AUTO
EXPOSURE subroutine 700. The auto exposure subroutine 700 will be
described hereinafter in greater detail.
After the exposure subroutine 700 has been executed at the call
step 620, the program advances to a call step 622 that calls an
AUTO-FOCUS subroutine 800. The AUTO-FOCUS subroutine 800 will be
described hereinafter in greater detail. Once the AUTO-FOCUS subroutine
800 has been executed the program proceeds to a go to command 624
that causes the program to go to a command step 606.
Considering again the decision step 604, if a determination is
made at the decision step 604 that the image capture switch 84 had
previously been fully depressed within T seconds, the image capture
routine 600 proceeds to the command step 606 that causes the partially
reflective partially transmissive mirror 42 to be pivoted out of
the primary light path for t milliseconds. The time period t milliseconds
is a sufficient period of time to permit the image sensor 34 to
capture the light indicative of an object image and to convert the
captured light into an electrical signal indicative of the object
image. In this regard, when the mirror 42 is pivoted out the primary
light path and into the secondary light path blocking the user from
seeing the object image passing through the primary lens.
Next, the routine 600 proceeds to a decision step 607 to determine
whether the exposure of the camera 10 was set when the auto exposure
subroutine 700 was previously executed. If the exposure of the camera
was not previously set when the mirror 42 was disposed in the primary
light path30, the routine 600 proceeds to the call command 609 that
calls the auto exposure subroutine 700. When the auto exposure subroutine
700 has been successfully executed, the subroutine 700 exists to
a command step 608.
Considering again the decision step 607, if the exposure of the
camera 10 was previously set when the mirror 42 was disposed in
the primary light path30, the routine 600 proceeds directly to the
command step 608 without calling the auto exposure subroutine 700
as previously described. Command step 608, causes the image sensor
34 to be activated for a sufficient period of time to convert the
light reflecting from the object image into a binary electrical
signal. Once the binary signal indicative of the object image has
been generated by the image sensor 34, the routine 600 proceeds
to a command step 610 that causes the binary signal to be stored
in the storage system 38. The command 610 also causes the path selecting
mirror 46 to be pivoted into the through the lens or secondary light
path 50 to permit the user to view the screen of the micro display
44.
When the path selecting mirror 46 has been pivoted into the secondary
light path 50, the routine 600 causes proceeds to a command step
612 that causes the object image immediately stored in the storage
system 38 to be retrieved and transferred to the micro display unit
44. In this manner the user is able to immediately view the captured
object image without changing the operating mode of the camera from
a preview mode to a review mode.
Next, the routine 600 proceeds to a decision step 614 to determine
whether the user has released the image capture switch 84. If the
user has not released the capture switch 84, the program will wait
at the decision step 614 until the switch 84 is released. When the
switch 84 is released, the routine advances to a command step 616
that causes the mirrors 42 and 46 to be returned to their initial
positions. Also at the command step 616 a program timer is activated
to facilitate determining whether the auto exposure and auto focus
algorithms 700 and 800 need to be executed again as previously described
with reference to the decision step 604. Once the program timer
has been set, the control program 600 proceeds to an end command
618 to exit the routine 600 and wait for the user to once again
activate the capture image switch 84.
Considering now the auto exposure algorithm 700 in greater detail
with reference to FIG. 10, when the auto exposure algorithm 700
is called from step 620 (FIG. 6) the auto exposure subroutine advances
from a start command 702 to an initiate capture command 704. The
initiate capture command enables the image sensor 34 to generate
a exposure calibration signal indicative of the ambient light conditions
seen through the primary lens 24. In this regard, the signal generated
by the image sensor 34 is indicative only of a portion of the entire
image seen through the primary lens 34.
The subroutine then advances to a subdivide command 706 that causes
the exposure calibration signal to be subdivided in a plurality
of gray level segments. As each segment is formed, the resulting
segment is stored via an arrange and store command 708. In this
regard, the segments may be stored in a matrix arrangement, a strip
of contiguous segments, or as sets of overlapping segments.
The subroutine then proceeds to a convert command 710 that retrieves
each segment and assigns each retrieved segment a binary value.
A binary one is established for a given segment if its gray level
value exceeds a predetermined luminance level of about eighteen
percent. If the given segment does not exceed the about eighteen
percent threshold value, the segment is assigned a binary zero value.
The assigning of binary values continues until all segments in the
arrangement have been assigned a one or zero value. The assigned
values are stored via a store command 712 and are subsequently utilized
as a pointer. The subroutine then advances to a set exposure level
command 714 where the microprocessor 36 retrieves an exposure value
that corresponds to a desired exposure setting based on the determined
pointer value. The retrieved exposure value is applied to the camera
10. The subroutine then goes to a return command 716 that returns
control to the main program at the call command 622 (FIG. 6).
Considering now the auto focus algorithm 800 in still greater detail
with reference to FIG. 9, when the auto focus subroutine 800 is
called from step 622 (FIG. 6) the auto focus subroutine advances
from a start command 802 to an initiate capture sequence command
804. The initiate capture sequence command 804 causes a sampling
period of T.sub.1 seconds to be subdivide into a plurality of t.sub.1
sampling periods, to cause a sequence of images to be captured.
In this regard, one image will be captured and temporarily stored
at each t.sub.1 occurrence. The algorithm then advances to a command
step 806 that causes the primary camera lens to move from an initial
hyperfocal position to a full range focusing position during the
sampling period T.sub.1. From the foregoing it should be understood
by those skilled in the art that as the primary lens system is moving
over its full focusing range a series of images with different focus
characteristics are being captured.
The subroutine then proceeds to a determination step 808 to determine
whether the primary lens system has advanced through its full focus
range. If the lens has not been moved through its full range the
subroutine advances to a command step 810 that causes a current
image as viewed through the primary lens to be temporarily stored.
The subroutine then returns to the determination step 808. From
the foregoing it should be understood by those skilled in the art
that as the primary lens system is moving over its full focusing
range, different ones of the images captured are being temporarily
stored.
Once a determination is made that the primary lens has moved over
its full range of motion, the subroutine advances from determination
step 808 to a return lens command 812. The return lens command 812
causes the primary lens to be returned to its initial hyperfocal
position.
After the return command 812 has been executed the subroutine advances
to a calculate command 814 that calculates a focus factor for each
of the temporarily stored images in order to determine which one
of the captured image has the best focus factor. In this regard,
the subroutine advances to a store command 816 that causes a current
focus factor to be stored if it is indicative of a better focused
image then that of a previously stored image. The subroutine then
goes to a determination step 818 to determine whether the primary
lens has returned to its initial hyperfocal position.
If the primary lens has not returned to its initial hyperfocal
position, the subroutine returns to the calculate step 814 and proceeds
as described previously. If the primary lens has returned to its
initial hyperfocal position, the subroutine advances to a determination
step 820 to determine whether a best focused position has been determined.
If a best focused position has not been determined, the program
advance to a return step 824 that returns the subroutine to the
main control program at the go to step 624 (FIG. 8). If a best focused
position has been determined, the program advances to a move lens
command 822 that causes the primary lens to move to its best focused
position. Once the lens has been moved to a best focused position,
the subroutine proceeds to the return step 824.
Considering now the camera 10 in still greater detail with reference
to FIG. 7, the status display 72 is mounted in the top side of the
camera housing 12 for viewing by the camera user. The display 72
is preferably a liquid crystal display that can display alphanumeric
and graphical information. The display 72 is driven in a conventional
manner by a display driver circuit 70 that will not be described
hereinafter in greater detail. The display driver 70 is coupled
to the microprocessor 26 via the bus 80 as best seen in FIG. 7.
The display driver 70 is also coupled to the micro display 44 on
which the recorded images are displayed each time the user actuates
the image capture switch 84 while the camera 10 is operated in an
image capture mode of operation. The micro display 44 also displays
menu information when the camera is operated in a menu mode of operation.
In this regard, when the camera is operated in the menu mode of
operation, the user via the scroll switches 86 and 88 can scroll
through the images stored in the storage system 38 and view menu
selection items for the purpose of downloading selected ones or
all of the stored images via the universal system bus 26, or deleting
one or all of the stored images. In short then, the micro display
44 can display a series of menus providing a plurality of command
options that can be selected by the user as part of a graphical
user interface (GUI) generated by the microprocessor 36 using a
control program stored in the internal memory 38.
The manually actuable controls 86 and 88 may be depressed to scroll
up and down through the command options displayed on the micro display
44 to provide the GUI. The pushbutton 86 when depressed in the menu
mode of operation causes the micro processor 36 under the commands
of the control program stored in the internal memory 38 to select
command options that are highlighted on the display screen of the
micro display 44.
While preferred embodiments of the present invention have been
described and illustrated herein, it should be understood by those
skilled in the art that the invention may be varied in both arrangement
and detail. Therefore, the protection afforded the present invention
should only be limited in accordance with the claims that follow. |