Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1998-03-18
2001-01-16
Lee, Cheukfan (Department: 2722)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S488000, C358S497000
Reexamination Certificate
active
06175429
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a document reader for optically reading a document to be converted into an electric signal and a method for adjusting its focus.
2. Related Art
A document reader is known which optically reads a color document by an image sensor of a storage-type charge transfer device such as CCD and color-decomposes the document thus read to acquire image data.
FIG. 13
is a schematic diagram of a conventional document reader in a mirror movement system. A document reader, generally
100
′ includes a reading unit
1
for optically reading a document to be electrically converted into multi-value (or binary) data, a data detecting unit
2
for detecting an output data from said read unit
1
, a controlling unit
3
for receiving the detected data from the data detecting unit
2
to produce an image data and controlling the movement of a mirror carriage
12
and mirrors
15
,
16
arranged in the reading unit
1
, and an interface
4
for outputting the image data. The image data is supplied to an external image data processing unit
6
such as a PC (personal computer) through the interface
4
and a cable
5
. Incidentally, in many cases, the controlling unit
3
is configured by an MPU (microprocessor having a CPU, RAM and ROM).
The reading unit
1
includes a document stand
11
on which a document or original is placed, a mirror carriage
12
which is a pair of a light source
13
and a mirror
14
used to scan the document optically; mirrors
15
,
16
; a light-gathering lens
17
, a CCD
18
and a stepping motor
21
for driving the mirror carriage
12
and mirrors
15
,
16
.
In
FIG. 13
, assuming that the distance between a face of the document and the mirror
14
is a, that between the mirrors
14
and
15
is b, that between the mirrors
15
and
16
is c, and that between the mirrors
16
and the light-gathering lens
17
is d, and a+b+c+d=L, even when the mirror carriage
12
and mirrors
15
,
16
move in a sub-scanning direction (direction of arrow
28
) in document reading, the total L of the optical path from the document face to the light-gathering lens
17
is constant.
Specifically, after the mirror carriage
12
and mirrors
15
,
16
have moved, the respective distances become a, b′ c and d′. In this case, the mirrors
15
,
16
move in the sub-scanning direction in synchronism with the movement of the mirror carriage
12
so that a+b′+c+d′=L, and the moving distance of the mirrors
15
,
16
is equal to the moving distance of the mirror carriage
12
×(½). For example, by setting a gear ratio for 2:1, the moving distance of the mirror is determined. Additionally, the light-gathering lens
17
and CCD
18
remain fixed and does not move in response to the scanning of the document.
As described above, the document reader
100
′ is designed so that the total L of the optical path is constant. In this case, L commonly contains a permissible error E. If the sum &dgr; of errors is larger than the permissible error E, an adjustment was made in only fabrication so that |&dgr;|≦E.
However, with an improvement of an image processing technique, a high resolution has been demanded for the color document reader so that the range of the permissible error E has been limited. Therefore, it has become difficult to absorb such an error only by techniques in design and fabrication inclusive of an improvement in material and accuracy of a motor of moving the mirrors and others. As a result, the requirement of high accuracy in the document reader has led to necessity of allowing for an increase in the production cost.
For example, in the case of the color document reader, the permissible error of E=2 mm or so has been traditionally required.
At the present time when the resolution has been improved, however, E≦0.5 mm, preferably E≈0 is required.
In the reader in which the document to be read is in contact with the document stand
11
, the distance a between the document and mirror
14
has been regarded as constant, thus providing no problem.
On the other hand, in a flat bed type document reader as shown in
FIG. 13
in which the document is a negative or positive film, the film, while it is held in a holder as shown in
FIG. 5
, is scanned.
In this case, a gap h (2-3 mm) due to the thickness of the holder is produced between the film and the document stand
11
. This led to a problem of making it more difficult to realize the permissible error E=&dgr;+&agr;≦0.5 mm. If the thickness of the holder is constant, this problem can be solved in hardware. However, in many cases, unfortunately, there was an inconvenience that the thickness of the holder varies according to manufactures and/or kind of the film to be held by the holder.
SUMMARY OF THE INVENTION
The present invention has been accomplished by inventors under an idea that the errors to be generated in manufacturing and transferring and a change in the distance between the document face and document stand (i.e. between the document and mirror
14
) can be absorbed by finely adjusting the optical path length L so as to absorb the errors &dgr;+&agr;, thus realizing focus adjustment.
The present invention has been accomplished in order to solve the above inconvenience on the basis of the above idea, and intends to provide a document reader in which the optical path length L is finely adjusted to make the focus adjustment and its focus adjusting method.
The document reader of the present invention includes a light gathering lens for gathering light from a document and an optical sensor for converting light from the light-gathering lens into an electric signal, an optical path length adjusting means capable of adjusting the optical-path length between said document and said light-gathering lens; and a controller for computing an average maximum value and an average minimum value of a luminance signal of each of pixels which are read by said optical sensor and issuing a command to said optical path length adjusting means so that a difference between said average maximum value and said average minimum value is maximum. In such a configuration, the optical path length from the document to the light gathering lens cancel errors such as variations in accuracy in fabrication, thereby providing an image data in focus.
The document reader of the present invention includes a light gathering lens for gathering light from a document and an optical sensor for converting light from the light-gathering lens into an electric signal, an optical path length adjusting means capable of adjusting the optical-path length between said document and said light-gathering lens; and a controller for computing an a difference between luminance signals at adjacent reading positions read by said optical sensor and issuing a command to said optical path length adjusting means so that the absolute value of the difference is maximum. In such a configuration, the optical path length from the document to the light gathering lens cancel errors such as variations in accuracy in fabrication, thereby providing an image data in focus.
The document reader of the present invention comprises a focus adjusting plate attached to a prescribed position of a document stand, and is characterized in that said controller issues a command to said optical path length adjusting means on the basis of a luminance signal of an image for focus adjustment on said focus adjusting plate which is read by said optical sensor. In such a configuration, the optical path length from the document to the light gathering lens cancel errors such as variations in accuracy in fabrication, thereby providing an image data in focus.
The focus adjusting method of the present invention is a focus adjusting method for a document reader which gathers light from a document by a light-gathering lens and converts light from said light-gathering lens into an electric signal, comprising the steps of: (
Nagaharu Kenichi
Nouda Noriyuki
Lee Cheukfan
Seiko Epson Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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