Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
1998-02-23
2004-03-09
Ho, Tuan (Department: 2612)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C348S308000
Reexamination Certificate
active
06704049
ABSTRACT:
BACKGROUND
The invention relates to color interpolation.
FIG. 1
shows a semiconductor imager
10
(e.g., a complementary metal-oxide semiconductor (CMOS) imager) might be used to electrically capture “snapshots” of an optical image. The imager is used to convert an optical image into an electrical representation. The imager
10
accomplishes this conversion through the use of an array of sensing elements arranged as pixel cells
12
that sense the intensity of light coming from the image. The “exposure time” for each snapshot depends on an integration interval during which each pixel cell
12
integrates an indication of the number of photons of light striking the cell
12
(i.e., measures an intensity of light striking the cell
12
) and provides an indication of the integrated value via an analog output signal. For CMOS imagers, on-chip analog conditioning circuitry
14
(e.g., circuitry to perform correlated double sampling and gain control) and an analog-to-digital converter (ADC)
16
process the analog outputs of the pixel cells
12
to provide a digital representation of the image which can be retrieved from the imager
10
through a parallel port interface
18
.
The pixel cells
12
provide an indication of the intensity of light striking the cell
12
. Hence, the above-described arrangement may be used to produce a monochrome or luminance only representation of the image. However, to produce color representations of the image, the imager also needs to provide information about primary colors (e.g., red, green and blue colors) of the image. To accomplish this, each pixel cell
12
is configured to sense the intensity level of light in one of the primary color bands. A typical way to accomplish this is to cover each pixel cell
12
with a spectrum-discriminating filter (e.g., a filter that only allows a red, green or blue color band to pass through the filter). As a result, some pixel cells
12
sense red light, some pixel cells
12
sense green light and some pixel cells
12
sense blue light. As an example, a multi-band filter pattern
20
(see
FIG. 2
) placed over the array of pixel cells
12
may have alternating red, green and blue filter stripes that extend along the columns of the array. Thus, each filter stripe of the pattern
20
configures one of the columns of the array to sense light in one of the primary color bands. As another example, the filter pattern may be checkered, instead of striped.
Each pixel cell
12
captures a portion of the image. To maximize the resolution of the image when reproduced on a display, it is desirable to form a one-to-one correspondence between the pixel cells
12
of the imager
10
and pixels of the display. However, with color imagers, three adjacent pixel cells
12
(each pixel cell
12
sensing a different primary color band) are typically used to provide the information needed to form one pixel on the display. Thus, when used to capture color images, the effective display pixel resolution of the imager
10
typically is one third of the actual pixel cell
12
resolution.
For purposes of preserving a one-to-one correspondence between the pixel cells
12
and the pixels of the display, one solution is to form an imager having three times as many pixel cells as corresponding pixels of the display to compensate for the three primary colors. Referring to
FIG. 3
, another solution is to use three imagers
22
,
24
, and
28
, one for each primary color band of the image. Thus, for example, one imager
22
(covered by a red filter) senses red light, one imager
24
(covered by a green filter) senses green light, and one imager
26
(covered by a blue filter) senses the blue light coming from the image. Dichroic plates
28
may be used to split the light into beams into its primary colors.
Referring to
FIG. 4
, a third solution might be to use an off chip discrete-time signal processing (DSP) engine
30
to interpolate the two missing colors for each pixel cell
12
. To accomplish this, the DSP engine
30
processes the color information provided by adjacent pixel cells
12
. Typically, nearest neighbors are weighted with predetermined coefficients and averaged to determine a color at a particular pixel cell location. For example, referring back to
FIG. 1
, a pixel cell
12
a
that is covered by a red filter provides a representation of a red color of the portion of the image striking the cell
12
a
. To ascertain the blue color of the portion of the image otherwise striking the cell
12
a
(if not for the red filter), the DSP engine
30
averages (a weighted representation of) the outputs of adjacent pixel cells
12
b
and
12
c
(i.e., adjacent pixel cells covered by a blue filter) to interpolate the missing blue color. The DSP engine
30
also interpolates the green color of the portion of the image that would other strike the cell
12
a
in a similar manner.
SUMMARY OF THE INVENTION
In general, in one aspect, the invention features an imager that has first and second photosensitive sites and an interpolator located in a semiconductor substrate. The first photosensitive site is configured to receive light having a spectral component, and the second photosensitive site is configured to measure the level of the spectral component in light received by the second photosensitive site. The interpolator is configured to estimate the level of the spectral component in the light received by the first photosensitive site based on the measurement by the second photosensitive site.
Implementations of the invention may include one or more of the following. The first and/or second photosensitive sites may include a pixel cell and a filter that covers the pixel cell. The filter covering the first photosensitive site may be configured to prevent the spectral component from striking the pixel cell, and the filter covering the second photosensitive site may be configured to allow the spectral component to strike the pixel cell. The first photosensitive site may also be configured to measure the level of another spectral component in light received by the first photosensitive site, and the interpolator may be also configured to estimate the level of another spectral component in the light received by the second photosensitive site based on the measurement by the first photosensitive site.
The imager may also include a third photosensitive site (also located in the substrate) that is configured to measure the level of the other spectral component in light received by the third photosensitive site. The first photosensitive site may also be configured to receive light having the another spectral component, and the interpolator may also be configured to estimate the level of the spectral components in the light received by the first photosensitive site based on the measurements by the second and third photosensitive sites.
In general, in another aspect, the invention features an imager that has first and second photosensitive sites and an interpolator located in a semiconductor substrate. Each first photosensitive site is configured to receive light having a spectral component, and each second photosensitive site is configured to measure the level of the spectral component in light received by the second photosensitive site. The interpolator is configured to estimate the level of the spectral component in the light received by at least one of the first photosensitive sites based on the measurements by the second photosensitive sites.
Implementations of the invention may include one or more of the following. The interpolator may include an averaging circuit that is configured to perform the estimation by averaging some of the measurements by the second photosensitive sites. The interpolator may also include a scaling circuit that is configured to scale some of the measurements by predetermined coefficients before being averaged by the averaging circuit. The scaling circuit may be programmable to change one or more of the coefficients. The first and second photosensitive sites may be part of an array of photosensitive sites (e.g., located in a co
Dickstein , Shapiro, Morin & Oshinsky, LLP
Ho Tuan
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