Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
1998-12-15
2003-11-25
Christensen, Andrew (Department: 2615)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C348S273000, C348S272000, C348S266000, C348S280000, C358S482000, C358S483000, C358S513000, C358S514000
Reexamination Certificate
active
06654056
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to photosensitive chips for creating electrical signals from an original image, as would be found, for example, in a digital scanner, copier, facsimile machine, or other document generating or reproducing device.
BACKGROUND OF THE INVENTION
Image sensor arrays typically comprise a photosensitive array of photosites which raster scan an image bearing document and convert the microscopic image areas viewed by each photosite to image signal charges. Each photosite includes one or more photodiodes, photogates or other photodetection devices. Following an integration period, the image signal charges are amplified and transferred as an analog video signal to a common output line or bus through successively actuated multiplexing transistors.
For high-performance image sensor arrays, a preferred design includes a photosensitive array of photosites of a width comparable to the width of a page being scanned, to permit one-to-one imaging generally without the use of reductive optics as taught in U.S. Pat. No. 5,473,513. In order to provide such a “full-width” array, however, relatively large silicon structures must be used to define the large number of photosites as shown in
FIG. 1. A
preferred technique to create such a large array is to assemble several photosensitive chips
10
1
through
10
N
end to end on a base substrate
20
, each chip
10
defining a small photosensitive array thereon. The base substrate
20
is preferably a form of ceramic such as alumina, and the chips
10
are preferably made of silicon or another semiconductor material. N is defined as any whole number.
Alternatively, chip
10
may represent a charged-coupled device (CCD) or another type of photosensitive semiconductor chip.
The chips
10
, which are assembled end to end to form one full-width array, are created by first creating the circuitry for a plurality of individual chips
10
on a single silicon wafer. The silicon wafer is then cut, or “diced,” around the circuit areas to yield discrete chips
10
. Typically, the technique for dicing the chips
10
includes a combination of chemical etching and mechanical sawing. Because, on each chip
10
, the photosites are spaced with high resolution from one end of a chip
10
to the other, the cutting of the chips
10
from the wafer requires precision dicing. It would be desirable to dice each individual chip
10
with a precise dimension along the photosensitive array of photosites, so that, when a series of chips
10
are assembled end-to-end to form a single page-width photosensitive array, there is a minimum disruption of spacing from an end photosite on one chip
10
to a neighboring photosite at the end of a neighboring chip
10
. Typically, there is a small gap
30
between two adjacent chips
10
. Ideally, the geometric centers of the photosites should be collinear and the photosites should be uniformly spaced across an entire full-width photosensitive array regardless of the configuration of silicon chips
10
forming the photosensitive array. In the prior art, photosites in the chips
10
were made in a square or rectangular shape to provide a repetitive structure of photosites
40
. In this way, the repetitive structure was maintained on a chip-to-chip basis, particularly in the gaps
30
between adjacent chips
10
as shown in FIG.
2
.
As shown in
FIG. 2
, the photosites
40
typically have a rectangular shape, wherein each photosite
40
is smaller in the x-direction (fast scan direction) than the y-direction (slow scan direction or direction of document motion) to allow for electrical isolation, to limit cross talk and to allow for conductive traces to run between photosites. As a result, the optical modulation transfer function (MTF) of the system is higher in the x-direction (fast scan direction) than in the y-direction (slow scan direction). The fact that the document to be scanned moves in the y-direction further reduces the y-MTF. However, the negative consequences of the high x-MTF need to be addressed.
For example, half-tone documents typically have a certain dot frequency in the x-direction. Since a beat occurs between the dot frequency and the frequency of the photosite locations, undesirable Moiré patterns appear on the reproduced documents. Therefore, there is a need for a new photosensitive array of photosites, which reduces or eliminates the Moiré patterns particularly in the x-direction (fast scan direction).
As shown in
FIG. 3
, there were attempts in the prior art to improve image quality at the boundary of adjacent chips by providing photosites having two different shapes on photosensitive chips. This pattern was generally disclosed in U.S. Pat. No. 5,552,828. The regular photosites
60
have a generally square shape or slightly rectangular shape whereas the end photosites
70
have a trapezoidal shape. The advantage of the generally trapezoidal shape of end photosites
70
is that, while the overall width of each end photosite
70
is equal to that of each regular photosites
60
, the geometric center of the end photosites
70
is made slightly closer to the edge of the chip
10
to help compensate for any chip spacing problems between the chips
10
. However, this arrangement of shapes does not reduce or eliminate Moiré patterns.
U.S. Pat. No. 5,031,032 discloses a pattern of photosites for a full width photosensitive array with photosites of different colors. Although multiple geometric shapes are used to form a rectangular photosite with the three different primary colors, this arrangement of shapes does not reduce or eliminate Moiré patterns.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a photosensitive array having a fast scan direction and a slow scan direction, wherein the photosensitive array includes an array of complementary shaped photosites on a chip, wherein the largest dimension of at least one photosite on a chip in the fast scan direction is longer than a pitch between two adjacent photosites in the fast scan direction. Preferably, the largest dimension of each photosite on a chip in the fast scan direction is longer than a pitch between two adjacent photosites. The photosensitive array may be a linear array or a two dimensional array. The array preferably extends from one end of the chip to the other, and the array of complementary shaped photosites is preferably buttable. The array can be used in single chip applications. However, the complementary shaped photosites on a chip are preferably adapted for end to end assembly with like arrays on like chips to form a full width array.
According to the present invention, there is provided a photosensitive array having a fast scan direction and a slow scan direction, wherein the photosensitive array includes an array of complementary triangular, trapezoidal or pentagonal shaped photosites on a chip extending from one end of the chip to the other. The photosensitive array reduces the modulation transfer function in the fast scan direction to reduce Moiré patterns. Each photosite has a photodetection device such as a photodiode or photogate and each photosite has the same surface area. A photosensitive array can be mounted on a substrate adjacent to a second photosensitive array of complementary shaped photosites wherein the last shape of the photosensitive array and the first shape of the second photosensitive array are complementary. A plurality of the photosensitive arrays can be juxtaposed and mounted on a rectangular substrate to form a full width photosensitive array. In several embodiments, the photosensitive arrays on the chips are buttable. The photosensitive array may be a linear array or two dimensional array. Further, the photosensitive array may be used independently to scan an image or can be juxtaposed with one or more photosensitive arrays to scan an image.
According to the present invention, there is provided a photosensitive array having a fast scan direction and a slow scan direction, wherein the photosensitive array includes an array of interlocking photosites
Feng Xiao-Fan
Hosier Paul A.
Perregaux Alain E.
Tandon Jagdish C.
Triplett Roger L.
Christensen Andrew
Daebeler P.
Genco Brian C
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