Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
2000-02-09
2004-05-18
Coles, Edward (Department: 2622)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S482000, C358S483000, C250S208100, C250S226000
Reexamination Certificate
active
06738164
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a color image reading apparatus and, more particularly, it relates to a color image reading apparatus adapted to separate a light beam coming from a color image into a plurality of light beams having respective wavelengths different from each other by means of a diffraction grating and receive the light beams produced by the separation by means of at least three line sensors.
2. Related Background Art
Various color image reading apparatus have been proposed to date for reading digitized color image information from the output signal of a line sensor by forming a color image of an original on the line sensor having light receiving pixels arranged one-dimensionally along the main scanning direction of the apparatus by way of an optical system. Charge coupled devices (CCDs) are typically used for the line sensor.
FIG. 1
of the accompanying drawings is a schematic cross sectional view of a principal portion of a known color image reading apparatus taken along the sub-scanning direction thereof. In
FIG. 1
, the X-axis is arranged along the main scanning direction while the Y-axis is running along the sub-scanning direction that rectangularly intersects the main scanning direction. Referring to
FIG. 1
, the light beam of a color image coming from the surface of the original
61
is converged by a focussing lens
62
and separated into the three primary colors of red (R), green (G) and blue (B) by means of a 3P prism. Then, the light beams of the three primary colors are focussed respectively on line sensors
64
,
65
and
66
. Each of the line sensors has a plurality of detecting elements (light receiving pixels) arranged one-dimensionally along the main scanning direction so that the color image information is read from each of the light beams having different wavelengths as the color image is scanned along the sub-scanning direction by means of a scanning means such as a mirror (not shown).
However, a known color image reading apparatus as illustrated in
FIG. 1
requires the use of a 3P prism that is prepared through an elaborate process to make the apparatus complex and costly. Further more, it is accompanied by various other problems including that the light beams produced by separate the incoming light beam by means of a 3P prism and the respective line sensors have to be positionally adjusted independently to make the entire operation of assembling the apparatus and regulating the performance thereof a very cumbersome one.
FIG. 2
is a schematic cross sectional view of a principal portion of another known color image reading apparatus taken along the sub-scanning direction thereof. The components same as those of
FIG. 1
are denoted respectively by the same reference symbols and would not be described any further. In the apparatus of
FIG. 2
, the 3P prism of
FIG. 1
is replaced by a pair of color separating beam splitters
74
and
75
provided with a wavelength selecting transmission film and adapted to divide the light beam converged by the focussing lens
62
into three light beams of the three primary colors that are separated from each other. The divided and separated three light beams are then focussed respectively on the three component line sensors of a monolithic 3-line sensor unit
73
arranged on the surface of a same substrate. Then, the color image information is read from the light beams having different wavelengths as the color image is scanned along the sub-scanning direction by means of a scanning means such as a mirror (not shown).
With the color image reading apparatus of
FIG. 2
, if the beam splitters
74
and
75
have a thickness of x, the distance separating the line sensors will be equal to 22x. Then, if the desired distance separating the line sensors is between 0.064 and 0.2 mm, the beam splitters
74
and
75
should be made to show a thickness x between 23 and 70 &mgr;m.
Normally, it is highly difficult to prepare beam splitters that have such a small thickness and still maintain optically excellent planeness. Therefore, it is also highly difficult for an apparatus as shown in
FIG. 2
to focus light beams on the respective line sensors without reducing their optical effectiveness.
FIG. 3
is a schematic cross sectional view of a principal portion of still another known color image reading apparatus taken along the sub-scanning direction thereof. The components same as those of FIG.
1
and
FIG. 2
are denoted respectively by the same reference symbols and would not be described any further. In the apparatus of
FIG. 3
, the color image on the surface of the original
61
is read only by means of an objective lens
62
and a monolithic 3-line sensor unit
73
same as that of FIG.
2
.
FIG. 4
is a schematic perspective view of the monolithic 3-line sensor unit
73
.
Referring to
FIGS. 3 and 4
, the monolithic 3-line sensor unit
73
has three component line sensors
81
,
82
and
83
arranged in parallel with each other on a same substrate. Each of the line sensors typically comprises a charge coupled device having a plurality of detecting elements (light receiving elements) arranged one-dimensionally along the main scanning direction. If the line sensors
81
and
82
are separated from each other by a distance of S
1
and the line sensors
82
and
83
are separated from each other by a distance of S
2
, both S
1
and S
2
are normally made to take a value between 0.064 and 0.2 mm in view of various manufacturing conditions. If the detecting elements (light receiving elements)
84
of the line sensors have a width W
1
in the main scanning direction and a width W
2
in the sub-scanning direction, they are normally made to take a value between 8 and 10 &mgr;m. If W
1
and W
2
are made equal to each other, a single detecting element may be made to have a size of 8 &mgr;m×8 &mgr;m or 10 &mgr;m×10 &mgr;m. The line sensors
81
,
82
and
83
are provided thereon with color filters for transmitting only light beams of blue (B), green (G) and red (R) respectively.
Generally, the gap S
1
separating the line sensors
81
and
82
and the gap S
2
separating the line sensors
82
and
83
are made equal to each other and also equal to the value of the pixel size W
2
along the sub-scanning direction as shown in
FIG. 4
multiplied by an integer for the reason as described below. Referring to
FIG. 3
, if only a focussing lens
62
is used to read the color image by means of a monolithic 3-line sensor unit as described above, the three line sensors
81
,
82
and
83
will read the original
61
simultaneously at three different respective positions
81
′,
82
′ and
83
′. Then, it is impossible to read simultaneously the signal components of the three primary colors (R, G, B) at any point on the original
61
. This means that the signal components of the three primary colors have to be synthetically combined after reading them respectively by means of the three sensors.
This operation of synthetically combining the signal components of the three primary colors can be carried out advantageously by selecting each of the inter-line distances S
1
, and S
2
of the three line sensors so as to be equal to the pixel size W
2
multiplied by an integer and using a corresponding redundancy line memory in order to delay, for example, the G and R signals (signal components for G and R) relative to the B signal (signal component for B). Thus, generally, S
1
and S
2
are made equal to each other and to W
2
multiplied by an integer.
Meanwhile, there have been proposed apparatus comprising a monolithic 3-line sensor unit and adapted to read a color image at a same position for the three primary colors without delaying any of the signal components.
FIG. 5
is a schematic cross sectional view of a principal portion of such a known color image reading apparatus taken along the sub-scanning direction thereof. In
FIG. 5
, the components same as those of
FIG. 4
are denoted respectively by the same reference symbols and would not be described any fu
Arita Shinichi
Kondo Kazuyuki
Sato Hiroshi
Shimomura Hidekazu
Canon Kabushiki Kaisha
Coles Edward
Fitzpatrick ,Cella, Harper & Scinto
Safaipour Houshang
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