Photocopying – Projection printing and copying cameras – With focusing or projection screen
Reexamination Certificate
1999-01-19
2001-08-21
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
With focusing or projection screen
C355S040000, C250S208300, C358S448000
Reexamination Certificate
active
06278513
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reader and a digital copier, more specifically, an image reader capable of reading images at an arbitrary scanning resolution and a digital copier capable of copying at an arbitrary zoom ratio.
2. Description of the Prior Art
High-speed and multifunctional digital copiers have been available recently, and fast speed for first copy time is demanded in the processing of contraction or enlargement.
Hereinafter, an example of a conventional digital copier will be described with reference to
FIGS. 9 and 10
.
FIG. 9
is a block diagram showing the flow of image signals of a conventional digital copier. An image sensor
71
scans a document and converts reflected light from the document into an electric signal. An A/D converter
72
converts an analog image signal from the image sensor
71
to a digital image signal. An image processing circuit
73
performs image processing such as edge enhancement, trimming, and half-tone processing or editing processing with respect to the digital image signal. A line buffer memory
74
buffers the image signal from the image processing circuit
73
for speed adjustment for outputting the image signal to a laser driver
78
. The laser driver
78
drives a semiconductor laser
79
to output laser beams for formation of electrostatic latent images.
FIG. 10
shows a schematic structure of a conventional digital copier. The digital copier includes an image scanning part A and a laser printing part B. The image scanning part A includes an ADF (auto document feeder), a document table
0
, a constant speed unit
3
including an exposure lamp
1
and a first mirror
2
, a half speed unit
6
including a second mirror
4
and a third mirror
5
, a lens
7
, and an image sensor
8
.
The laser printing part B includes a laser scanner unit including a semiconductor laser, a polygon motor, a polygon mirror and a laser optical system, a mirror
41
, a photoconductor drum
9
, a main charger
10
, a developer
11
, a transfer charger
20
, a cleaner
35
, an electricity removal lamp
36
, a conveyer belt
30
, a fixer
31
, a guide
32
, a paper ejection roller
33
, paper feed rollers
12
,
13
, and
14
, a guide
18
, a timing roller
19
and a sorter
34
.
The operation of the conventional digital copier having the described structure will be described below. Aplurality of documents placed on the ADF
50
are fed one by one by the ADF and placed face down on the document table
1
formed of a transparent glass sheet. The document is exposed to light by the exposure lamp
1
. The first mirror
2
reflects the reflected light from the document in the direction of the second mirror
4
. The constant speed unit
3
including the exposure lamp
1
and the first mirror
2
scans the document while moving at a constant speed in the direction shown by arrow P. The second mirror
4
and the third mirror
5
reflect the reflected light from the first mirror
1
further. The half speed unit
6
including the second mirror
4
and the third mirror
5
moves at a speed half that of the constant speed unit
3
in the same direction as the constant speed unit
3
. The reflected light from the document is converged to the image sensor
8
by the lens
7
.
The image sensor
8
is a linear sensor that is longer in the direction perpendicular to the direction of the movement on the surface of the document. In the following description, an electric scanning direction along the longitudinal direction of the image sensor
8
is referred to as a primary scanning direction, and a mechanical scanning direction along the direction of the movement of the constant speed unit
3
is referred to as a secondary scanning direction.
The photoconductor drum
9
rotates at a constant speed in the direction shown by arrow R. The main charger
10
charges the photoconductor drum
9
uniformly. The laser beams radiated from the laser scanner unit
40
is reflected at the mirror
41
for exposure and scanning on the photoconductor drum
9
so that electrostatic latent images are formed on the photoconductor drum
9
. The developer
11
develops the electrostatic latent images with toner, and forms toner images on the photoconductor drum
9
. In the photoconductor drum
9
, a direction parallel to the rotation axis corresponds to the primary scanning direction, and the rotation direction of the photoconductor drum corresponds to the secondary scanning direction.
Recording paper cassettes
15
,
16
, and
17
hold a plurality of recording papers. The recording paper cassettes each hold different types of recording papers. The recording paper cassettes are removable so that the cassettes holding recording papers having necessary size and direction are removably mounted to the copier. The paper feed rollers
12
,
13
and
14
feed one recording paper at a time from the recording paper cassettes. The guide
18
guides the fed recording paper to the ting roller
19
. The timing roller
19
adjusts feed timing and performs registration so that the toner images on the photoconductor drum
9
are on the fed recording paper.
The toner images on the photoconductor drum
9
are transferred onto the recording paper by an electric field generated by the transfer charger
20
. The conveyer belt
30
moves in the direction shown by arrow Q and conveys the recording paper with the toner images transferred to the fixer
31
. The fixer
31
fixes the toner images onto the recording paper by heat. The recording paper with the images fixed thereon is guided by the guide
32
to the paper ejection roller
33
. The paper ejection roller
33
ejects the paper to the sorter
34
. The sorter
34
is provided with a plurality of paper ejection trays (bins) and performs gathering for each set of copies mechanically. The sorter
34
also includes a staple function and a punch function.
Toner that remains on the photoconductor drum
9
is removed by the cleaner
35
. Then, the electricity removal lamp
36
radiates light to the photoconductor drum
9
so that the charges on the photoconductor drum disappear.
Given such a sequence of operations in the image scanning part and the printing part, the primary scanning cycle in the image scanning part is equal to the primary scanning cycle of the printing part. Therefore, copying with contraction or enlargement in the secondary scanning direction can be achieved by changing the secondary scanning speed of the printing part or the image scanning part. Typically, copying with contraction or enlargement in the secondary scanning direction is performed by allowing the secondary scanning speed of the printing part to be constant and the secondary scanning speed of the image scanning part to be different from that of copying in equal size. The relationship between the secondary scanning speed V
0
of the image scanning part for equal size copying and the secondary scanning speed V
Z
of the image scanning part for copying at a zoom ratio R is as follows:
V
Z
=V
0
/R.
This conventional method for contraction and enlargement copying is disclosed in Japanese Laid-Open Patent Publication No. 59-63868.
The minimum zoom ratio in the current digital copier is generally 33% or 25%. In the structure as described above, for example, in the case of copying at a contraction ratio of 33%, the image scanning part is required to scan in the secondary direction at three times the speed for equal size copying. In this case, it is necessary to design the torque of the motor and the secondary scanning mechanism so that the image scanning part can operate at a secondary scanning speed of three times the regular speed, in order to copy at the minimum zoom ratio, which is not frequently used. This is one factor that raises the cost.
Furthermore, in the case of a high-speed digital copier that can perform equal size copying at high speed, copying at a zoom ratio of 33% or 25% requires the image scanner to perform secondary scanning at excessively high speed, which is structurally difficult to realize. The
Hisatomi Kenji
Kuwano Hideyuki
Murata Kazuyuki
Okada Yuji
Takahashi Naoki
Adams Russell
Kim Peter B.
Matsushita Electric - Industrial Co., Ltd.
Rosenthal & Osha L.L.P.
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