Digital Camera Patent Abstract
A digital camera including a photosensor with a plurality of picture
elements that define an image resolution that is adjustable.
Digital Camera Patent Claims
What is claimed is:
1. A digital camera comprising: a lens for directing light into
said digital camera; a body connected to said lens, said body comprising
an exterior and an interior that houses a CMOS sensor having an
array of pixels defining an image resolution of said digital camera;
a microprocessor; a resolution selector provided on said exterior
that is operable by a user to vary said image resolution between
at least three different resolution settings to adjust low light
performance of said digital camera, such that the user can selectively
and dynamically adjust said image resolution at any time without
the need to access a menu system of said camera; image enhancement
apparatus comprising: an aperture disposed between said CMOS sensor
and said lens; an amplifier interposed between said microprocessor
and said CMOS sensor; and a shutter; wherein: the aperture, the
amplifier and the shutter are configured to be automatically adjustable
together via the microprocessor in any combination, as well as automatically
adjustable via the microprocessor independently of each other; and
wherein said resolution selector is configured to be operable by
the user independently of said image enhancement apparatus.
2. The digital camera as claimed in claim 1, wherein said microprocessor
controls said image resolution of said CMOS sensor responsive to
actuation of said resolution selector.
3. The digital camera of claim 2 wherein the resolution selector,
and the microprocessor, are further configured to enable the user
to adjust low light performance of said digital camera before, during,
and after the camera automatically corrects for low light level
via the image enhancement apparatus.
4. The digital camera of claim 3, and wherein the microprocessor
is further configured to adjust the image enhancement apparatus
responsive to adjustments made by the user via the resolution selector.
5. The digital camera of claim 1 wherein the resolution selector
is configured to adjust low light performance of said digital camera
by virtually changing a size of the pixels of the CMOS sensor via
the microprocessor, and prior to any application of the amplifier
to the image.
6. A method of imaging comprising: powering a digital camera such
that the camera is prepared to capture an image; adjusting, via
a user, an image resolution of the camera to one of at least three
different resolution settings using a resolution selector provided
on an exterior of the camera to lower the image resolution in low-light
conditions to improve the camera performance without increasing
noise, wherein the adjusting occurs without the need to access a
camera menu system; and following adjusting the image resolution
of the camera using the resolution selector, automatically adjusting
the image using an image enhancement apparatus, said image enhancement
apparatus comprising an aperture disposed between said CMOS sensor
and said lens, an amplifier interposed between said microprocessor
and said CMOS sensor, and a shutter.
7. The method of claim 6, wherein adjusting the resolution selector
is performed while the user is framing a view.
8. The method of claim 6, wherein the adjusting the resolution
selector is performed during camera focusing.
9. The method of claim 6, wherein the resolution selector is positionable
in at least three different resolution positions.
10. The method of claim 6, wherein adjusting the image resolution
using the resolution selector comprises summing photoelectric charges
of a group of pixels of a sensor of the digital camera to reduce
the image resolution.
Digital Camera Patent Description
The process of capturing images includes forming a visible image
of a subject on a photosensitive surface by introducing light or
other forms of radiation thereto. Image capturing devices are widely
used for videography, photography, infrared photography, ultraviolet
photography, stereoscopic photography, microphotography, and thermography.
Such devices generally include video cameras, film cameras, and
Cameras basically include a light-tight body having an image capturing
medium at a back end thereof, a shutter mechanism in front of the
image capturing medium, an aperture in front of the shutter, and
a lens disposed oppositely of the image capturing medium at a front
end of the camera. The lens focuses light from a photographic subject
through the aperture and shutter and onto the image-capturing medium
to form an image of the subject thereon. The shutter and aperture
together control exposure of the image-capturing medium. The shutter
controls the length of time the image-capturing medium is exposed
to light from the subject and the aperture is adjustable in size
to control the amount of light from the subject that impinges on
the image-capturing medium. Other camera features typically include
a viewfinder to show the photographic subject, flash units to illuminate
the photographic subject, and exposure meters to measure light.
Digital cameras are increasingly popular and technology advances
are rapidly resulting in increased performance capability. A digital
camera captures a subject, scene, or view in elemental portions
and generates an electronic signal that is representative of the
subject, scene, or view. Unlike conventional film cameras that use
a photoresponsive film as the image capturing medium, digital cameras
typically use electronic photosensors such as one or more charge
coupled device (CCD) chips. The CCD chips are configured to receive
light reflecting from the photographic subject and to convert the
reflected light into an electronic signal. A CCD chip includes an
array of very fine picture elements or "pixels" arranged
in horizontal rows and vertical columns.
Upon exposure to imaging light from a subject, the CCD chips collect
an array of discrete light energies or photon charges that correspond
to or map the photographic subject column-by-column, row-by-row,
and pixel-by-pixel such that a photon charge representation of the
subject is seized. The CCD uses off-chip electronic circuits to
process the photon charges and convert them into useful digital
signals that can be stored in electronic memory either on or off-camera.
Thus, digital cameras provide highly convenient features such as
instant picture display and electronic storage format among many
others, but provide image quality that is not as capable of handling
low-light conditions as that of conventional film cameras.
Image resolution in digital cameras continues to improve as CCD
chips with finer pixel sizes are developed that enable finer elemental
representations of a photographic subject. Unfortunately, finer
pixel size tends to adversely affect the already compromised low-light
performance of a digital camera. More particularly, the light sensitivity
or light gathering ability of a CCD decreases with reductions in
pixel size over a given surface area of the CCD. In other words,
for a CCD of a given surface area, the light gathering ability of
the CCD decreases with increases in pixel count. This is because
the CCD tends to lose optical sensing surface area to accommodate
the width of borderlines between adjacent pixels. The result is
increased image resolution via finer parsing of the view, but at
a cost of reduced light gathering ability and hence reduced low-light
Low-light performance in digital cameras has typically been adjusted
by varying the typical mechanical exposure settings of shutter speed,
and aperture size, and also by adjusting the electronic setting
of CCD output gain. One problem in varying shutter speed is a blurred
image caused by relative movement between the camera and photographic
subject while the shutter is open for a relatively long period of
time to let more light into the camera. Also, a problem in varying
gain is that increases in gain result in increases in noise and
corresponding decreases in image quality. Digital cameras combine
gain and exposure control into an automatic image enhancement feature.
Unfortunately, such features are still susceptible to blur and noise
problems and do not provide a user with readily accessible independent
and dynamic range control of the resolution and light gathering
ability of the image capturing medium.
One embodiment of the present invention may comprise a digital
camera including a means for directing radiant energy into the digital
camera and a means for capturing an image from the radiant energy.
The means for capturing includes a plurality of elements that define
an image resolution, and the embodiment further includes a means
for selectively and dynamically adjusting the image resolution.
Another embodiment of the present invention may comprise a digital
camera including a lens for directing radiant energy into the digital
camera and an image-capturing medium upon which the radiant energy
impinges. The image-capturing medium includes a plurality of pixels
that define an image resolution of the digital camera. A resolution
control selector is in communication with the image-capturing medium
to vary the image resolution.
Yet another embodiment of the present invention may comprise a
digital camera including a lens for directing light into said digital
camera and a body connected to the lens, wherein the body includes
a CMOS sensor having an array of pixels that define an image resolution
of the digital camera. A resolution selector is provided for varying
the image resolution to adjust low light performance of the digital
camera. The resolution selector is attached to at least one of the
lens and the body and is in communication with the CMOS sensor.
Still another embodiment of the present invention may comprise
a method of imaging including: directing radiant energy into a digital
camera; capturing an image from the radiant energy on a plurality
of elements that define an image resolution; and selectively and
dynamically adjusting the image resolution.
A further embodiment of the present invention may comprises a sensor
assembly including a CMOS photosensor having a plurality of pixels
arranged in a grid, and further including a light sensor that senses
ambient light levels and generates a control signal in response
thereto. A control system selectively groups pixels of the plurality
of pixels and sums signal outputs of selectively grouped pixels
of the plurality of pixels in response to the control signal.
Yet a further embodiment of the present invention may comprise
a digital camera having a CMOS photosensor having a plurality of
pixels arranged in a grid, and further including a light sensor
that senses ambient light levels and generates a control signal
in response thereto. A control system selectively groups pixels
of the plurality of pixels and sums signal outputs of selectively
grouped pixels of the plurality of pixels in response to the control
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a block diagrammatic view of a digital camera according
to an embodiment of the present invention.
FIG. 1A is a flow chart illustrating an alternative automatic function
of the digital camera according to an embodiment of the present
FIG. 2A is a partial view of an image capturing medium having an
unsummed array of pixels in the digital camera of FIG. 1.
FIG. 2B is a partial view of the image capturing medium of FIG.
2A wherein the array of pixels are summed into 2.times.2 groups.
FIG. 2C is a partial view of the image capturing medium of FIG.
2B wherein the array of pixels have been further summed from 2.times.2
groups into 4.times.4 groups.
Referring now in detail to the Figures, there is shown in FIG.
1 a block diagram of a digital camera 10 according to one embodiment
of the present invention. The digital camera 10 generally includes
a lens or lens assembly 12 attached to a body 14, and within the
body 14 there is a viewfinder 16, an aperture 18, a shutter 20,
and a stepper motor 22 for adjusting the lens assembly 12, aperture
18, and shutter 20. Also within the body 12 there is an image capturing
medium 24, a gain control device 26, an analog-to-digital (A-D)
converter 28, a digital-to-analog (D-A) converter 30, a microprocessor
32, a memory controller 34, an internal memory unit 36, and a memory
card 38. A display 40 and control panel 42 are provided on the body
12 for input/output with the user. Power is provided by a power
unit such as a battery (not shown).
The digital camera 10 is capable of operation in a variety of lighting
conditions ranging from the very bright sunlit outdoors to very
dimly lit or dark situations. Low-light performance of the digital
camera 10 is implemented in a variety of ways, as will be discussed
in greater detail below. In one embodiment, the digital camera 10
adjusts to low-light conditions by modifying one or more of the
following settings: size of the aperture 18, speed of the shutter
20, gain from the image capturing medium 24, and resolution capability
of the image capturing medium 24.
Starting at the front of the camera 10, the lens assembly 12 may
be an integral part of the body 14 or may be separately and removably
connected to the front thereof. In any case, the lens assembly 12
is used to direct radiant energy into the digital camera 10 by focusing,
isolating, or framing a selected subject, scene, or view of the
world from which emanates or reflects rays of energy. In other words,
the lens assembly 12 provides a conduit into which rays of light,
shown specifically at 11, are received and through which the rays
of light travel to the inside of the digital camera 10. The stepper
motor 22 couples to and adjustably drives the lens assembly 12 to
magnify, zoom, or otherwise enlarge the appearance of a framed view.
A light splitting device 13, such as a dichromic mirror, splits
and directs the incoming light 11 into a first light path 11a that
passes through the viewfinder 16 and a second light path 11b that
leads to medium 24. The viewfinder 16 is typically integrated within
the body 14 and is provided to optically communicate a framed view
of the world to a user looking into the viewfinder 16. This view
generally corresponds to an optical image projected onto the medium
24 by lens assembly 12.
The aperture 18 is located within the body 14 of the digital camera
10 along imaging light path 11b behind the lens assembly 12 and
variably regulates, over a range of opening sizes, the amount of
imaging light that passes through the lens assembly 12 into the
body 14 of the digital camera 10. The shutter 20 is mounted in the
imaging light path 11b behind the lens assembly 12 and aperture
18 and is a normally closed device that snaps open to let light
pass therethrough and impinge on the image capturing medium 24.
The stepper motor 22 is coupled to and adjustably drives the aperture
18 and shutter 20 independently or in combination with one another
to vary the exposure of the image-capturing medium 24 to imaging
light, which passes through the lens assembly 12, aperture 18, and
shutter 20. Accordingly, the low-light level performance of the
digital camera 10 can be regulated by increasing or decreasing the
exposure of the image capturing medium 24. But, increasing the exposure
of the image capturing medium 24 requires increased camera stability
while the digital camera 10 captures an image of a view. Alternatively,
the shutter 20 need not be a mechanical device, but rather can be
an electronic function of the image-capturing device. Regardless,
the function of the shutter 20 is to momentarily, over a variable
range of time, permit light to expose the photoresponsive elements
of the image-capturing medium 24.
The image capturing medium 24 may be a complimentary metal oxide
semiconductor (CMOS) sensor that is positioned behind the lens,
aperture, and shutter within the body of the camera. The image capturing
medium encompasses any device or material that is capable of capturing
radiant energy and at least partially capable of converting same
into an electronic signal that becomes a virtual representation
of the optical image projected onto the sensor 24 by the lens assembly
The image-capturing medium may be a CMOS sensor 24, which is a
photoresponsive device that includes very fine sub-elements, sub-sensors,
or pixels that are typically arranged in rows and columns to define
an array or grid. Upon exposure to light energy, or photons, reflecting
from a view and passing through the lens, aperture, and shutter,
each pixel of the array gets "filled" with a photoelectronic
charge that represents an elemental portion of a virtual representation
of the subject, scene, or view. The more pixels in an array, the
better the representation, or resolution, of the view. Digital camera
technology has progressed such that significant reductions in pixel
size, and thus, increases in resolution capability, have been achieved.
Today, CMOS sensors have a resolution of millions of pixels and,
for example, a four mega-pixel (4 Mp) sensor provides an array of
2,000 rows by 2,000 columns of individual pixels. CMOS sensors are
known in the art and examples of such are disclosed in the following
patents which are hereby incorporated by reference herein: U.S.
Pat. No. 6,215,113 to Chen et al., and U.S. Pat. No. 6,344,669 to
The gain control device 26 is connected the CMOS sensor 24 to amplify
the electronic signals therefrom. The gain control device 26 may
be a variable analog amplifier that is connected between the A-D
converter 28 and the CMOS sensor 24 to regulate the intensity of
the electronic signal passing from the CMOS sensor 24 to the microprocessor
32 via the A-D converter 28. The intensity of the signal is also
regulated by the microprocessor 32 via the D-A 30 converter that
is interposed the microprocessor 32 and gain control device 26.
The A-D converter converts the amplified analog signals from the
gain control device 26 into digital signals of acceptable levels
that are appropriate for the microprocessor 32.
The low-light level performance of the digital camera 10 can also
be regulated by the gain control device 26. The microprocessor 32
can signal the gain control device 26 to amplify the signal from
the CMOS sensor 24 to make up for a weak signal due to low-light
conditions, with some attendant amplification of inherent noise
from the CMOS sensor 24. The gain control device 26, aperture 18,
and shutter may be adjustable together in any combination or adjustable
independently to constitute an image enhancement apparatus that
is automatically controlled by the microprocessor 32.
The microprocessor 32 operates under control programs or software
that are stored in the internal memory unit 36 to which the microprocessor
32 is connected. The memory controller 34 is connected to the microprocessor
32 and internal memory unit 36 for controlling the handling of images
captured by the digital camera 10 and stored on the removable memory
card 38 which is removably plugged into the memory controller 34.
Such captured images are made available to the user for viewing
on the display panel 40 which is driven by the microprocessor 32.
The user sees a representative image of the view on the display
panel 40 and controls the digital camera 10 via the control panel
42 which are both communicated with the microprocessor 32 of the
digital camera 10. The display panel 40 can be an LCD screen, gas
plasma screen, or other display device.
The control panel 42 is attached to the body 14 of the digital
camera 10 and includes a set of control selectors including buttons,
switches, knobs, or the like, including a power on/off button 44,
a mode selection switch 46, zoom in--zoom out buttons 48 and 50,
a resolution control knob 52, and a shutter button 54. The resolution
control knob 52 can also be a dial, button, switch, and the like.
The resolution control knob 52 is a user input selector device
that provides the user the opportunity to selectively and dynamically
adjust image resolution among multiple different resolution settings
and at any time such as while framing a view, zooming a view, and/or
while the digital camera 10 is focusing or adjusting. Especially
in the case of low light conditions, the resolution control knob
52 is provided to independently and dynamically control the camera's
image resolution and, thus, the camera's low light performance,
by virtually changing the size of the pixels of the CMOS sensor
24 via the microprocessor 32 and D-A converter 30, as shown in FIG.
1 and as further described below with respect to FIGS. 2A-2C.
Alternatively, and still referring to FIG. 1, it is contemplated
that the resolution control could also be carried out in an automatic
mode using information from a light-level sensor 55 as input to
the microprocessor 32. The light-level sensor 55 senses the ambient
light conditions under which the digital camera 10 is operating,
and outputs a signal for use by the microprocessor 32 in deciding
how and how much to adjust low-light performance of the digital
camera 10. In turn, the microprocessor 32 outputs signals directly
to the stepper motor 22, and indirectly to the CMOS sensor 24 and
gain control device 26 via the D-A converter 30. Again, the microprocessor
32 operates under pre-programmed instructions that are loaded to
the internal memory unit 36 and communicated to the microprocessor
32. Such instructions, or software, can enable the microprocessor
32 to decide whether to adjust aperture size, shutter speed, CMOS
gain, or CMOS resolution, or any combination thereof, based at least
in part on input from the light-level sensor 55.
FIG. 1A charts the automatic mode of the present invention. At
step 110, the light-level sensor 55 measures the ambient light-level
of the environment in which the camera is operated. At step 120,
the light-level measurement is output to the microprocessor 32 of
FIG. 1, which at step 130 references a look-up table that is stored
in the internal memory 36 of FIG. 1. The look up table includes
information pertaining to changes in the level of light intensity
that can trigger an adjustment in CMOS pixel resolution. In this
respect, the resolution of the CMOS sensor may be varied substantially
incrementally in response to detected changes in the ambient light
level. For example, for a given light level measurement of X candelas,
the corresponding pixel resolution could be 1.times.1. For 0.5X
candelas the corresponding pixel resolution could be 2.times.2,
and so forth as shown in step 130. Once the microprocessor references
the correct pixel resolution for the measured light-level, a control
signal is output to the CMOS sensor to adjust pixel resolution as
reflected at step 140. It is contemplated that a fitting formula
or the like could be used to instruct the microprocessor and CMOS
sensor instead of the look up table.
Referring now to FIG. 2A, there is shown a portion of an array
of pixels 56 of the CMOS sensor 24, wherein each individual pixel
58 can be dimensionally characterized as 1.times.1 in horizontal
and vertical directions. Electronically, pixel size is virtually
adjustable wherein the pixels 58 are combinable together into groups
of 2, 3, 4, 8, or any other size group, as depicted in FIGS. 2B
and 20. If a view is insufficiently lit, a user can turn the resolution
control knob (shown in FIG. 1) to adjust the resolution and light
gathering ability of the CMOS sensor 24. In other words, the user
can turn the resolution control knob to sum the pixels 58 from 1.times.1
to 2.times.2 and vice-versa. The user can then reevaluate whether
further increases or decreases in resolution are necessary to yield
a desired image quality. Accordingly, FIG. 2B illustrates a portion
of the CMOS sensor 24 having pixels 58 summed into groups of 2.times.2
pixels 60, wherein a 2000.times.2000 pixel sensor would effectively
reduce to a 1000.times.1000 pixel sensor for improved light gathering
capability. Similarly, FIG. 2C illustrates a portion of the CMOS
sensor 24 wherein the pixels 58 have been summed into groups of
4.times.4 pixels 60, wherein a 2000.times.2000 pixel sensor would
effectively reduce to a 500.times.500 pixel sensor for even further
improved light gathering capability.
The summing process takes place on the CMOS sensor 24 itself and
entails combining two or more photoelectronic charges of a given
group of pixels. This has the effect of virtually increasing the
pixel size of a given sensor. For a 4Mp sensor then, pixel size
can be varied from 4,000,000 1.times.1 actual pixels, to 2,000,000
2.times.2 virtual pixels, to 1,000,000 4.times.4 virtual pixels,
etc., on up to one 2000.times.2000 virtual pixel. The result is
groups of net photoelectronic charges that equal the sum of the
individual photoelectronic charges of each group of summed pixels.
For light gathering purposes, summing provides increased signal-to-noise
ratio because the light gathering signal increases but the inherent
noise from the CMOS sensor 24 remains constant since the summing
function occurs before any gain is applied to the signal. Hence,
summing increases the light gathering ability of the CMOS sensor
24 at the acceptable expense of a proportional reduction in resolution
with no attendant increase in noise.
This tradeoff between light sensitivity and resolution is a net
benefit, especially in low light level situations and with or without
relying on the camera's automatic exposure and gain adjustment.
Now, a user is able to change the light gathering ability of the
camera under low-light level conditions before, during, and after
the camera automatically corrects for low light level via exposure
and gain control. Moreover, a user can flexibly or dynamically improve
the low light performance as desired and independently of any automatic
exposure and/or gain adjustments. In other words, a user can decide
whether to sacrifice image resolution in favor of improved light
gathering ability to arrive at a desired overall image quality,
independently of or simultaneously with other image enhancement
features such as gain and exposure compensation.
While the present invention has been described in terms of a limited
number of embodiments, it is apparent that other forms could be
adopted by one skilled in the art. In other words, claim elements
are not limited to the imperfections of the exact language used,
but encompass as well other structure that fulfills the same functional
purpose. In other words, the teachings of the present invention
encompass any reasonable substitutions or equivalents of claim limitations
except insofar as limited by the prior art. Those skilled in the
art will appreciate that other applications, including those outside
of the digital camera industry, are possible with this invention.
For instance, the present invention is applicable to apparatus associated
with videography, photography, infrared photography, ultraviolet
photography, stereoscopic photography, microphotography, thermography,
and the like. Accordingly, the present invention is not limited
to only digital cameras. Accordingly, the scope of the present invention
is to be limited only by the following claims.