Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2000-06-06
2003-05-06
Lee, Michael G. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462110, C235S462220, C235S462240, C235S462320
Reexamination Certificate
active
06557762
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method for adjusting the depth of scanning field to an optimally increased range. Especially, the invention is a scanner assembling method which increases and adjusts the depth of scanning field to an optimal range, Thus, the scanner can obtain good quality of scanning images even if the original document is wrinkled.
2. Background Description
Nowadays, the scanning mechanism and technology have improved dramatically. The scanning device is generally integrated to our daily life. Users can capture the images from documents and transfer the images to electrical files. Thus, the electrical files can be sent to others. Usually, the scanning device will employ some optical elements and scanning technologies. The employed optical technologies and elements are needed to be adjusted for scanning documents to acquire scanning images via a precise scanning mechanism. The scanning device is able to record the scanning image by an image generating means. In view of the above, the initial adjustment and assembly of the optical technologies and elements, are very important to the whole scanning processes.
Referring to
FIG. 2
, the traditional adjustment and assembly of a scanning device are illustrated as follows:
FIG. 2
shows the traditional adjustment and assembly of the scanning mechanism along with the chart of MTF (Modulation Transfer Function) and DF (Depth of Field) curve. The scanning mechanism
22
includes a glass plate
221
, lens
222
and an image generating means
220
. The correction document
24
is placed on the glass plate
221
.
Further,
FIG. 2
also shows the chart of MTF and the depth of field of scanning position. The value of MTF represents resolution of the scanning module of a scanning device. MTF is generated from a mathematical formula. Higher value of MTF means higher resolution. Lower MTF can be deemed as a lower resolution of the scanning module, and vice versa. Generally, the shape
200
of the MTF-DF curve varies from different characteristics of the scanning module
22
. Different positions of lens
222
also change the shape
200
of the MTF-DF curve. Therefore in the actual practice, the value of MTF should be kept above a certain value when the scanning module
22
is assembled. The certain value is shown in
FIG. 2
, as legend
201
. This value is generated by the acceptance of resolution by human eyes. If the value of MTF is maintained above legend
201
, the value of DF will range between the legend
204
and legend
205
. Thus, the range between legend
204
and legend
205
is defined the tolerance of DF, and be presented by legend
202
.
As stated in the above, when the scanning device is under adjusting process, a correction document
24
is placed on the glass plate
221
. There are drawings and lines in the correction document for adjusting the scanning image. The scanning device also includes a light source (not shown in the figure). The light source projects light to the glass plate
221
and the light is reflected by the correction document
24
. Thus, the reflected light, passes through an optical path
223
and lens
222
and finally been generated to a scanning image in a scanning generating means
222
. The scanning generating means
222
is a CCD (charged coupled device). By an output device (not shown in the figures), the correction technician will: know the value of the MTF. This value of MTF represents the resolution of the correction document
24
which is placed on the glass plate
221
. If the correction person adjusts the position of lens
222
, the shape
200
of MTF-DF will move upward or downward, following the changing position of lens
222
. In this way, the related MTF of the scanning module
22
will be achieved. Therefore, the correction person can adjust and fix the lens
222
to achieve the maximum value of MTF of the scanning module. The fixed position of the lens
222
is the best position to achieve the optimal resolution. This fixed position is also the optimal depth of field which is the legend
203
.
Recently, users ask higher quality and more functions to the scanning device. For example, scanning devices with increased optical resolution and ability to scan different scanning objects are preferred by the buyers. However, if the manufacturer would increase the optical resolution, the resolution of the image generating means (e.g., CCD) and lenses should be improved together. If the resolution of the lens is increased, the optical depth of field will be decreased and range of the depth of field
202
will be smaller. Therefore, if the scanning document is wrinkled, the wrinkled document will easily be out of the range of the depth of field
202
. Thus, the scanning image will be fizzy in this situation as illustrated in FIG.
1
A. As shown in
FIG. 1A
, a scanning object
12
is placed on a glass plate
10
. Because the scanning object
12
is not smooth, the portion
14
will easily be out of the range of the tolerant depth of field of the scanning device. Thus, the portion
14
is fuzzy. Moreover, if the scanning device is employed to scan books or magazines the same fuzzy effects will happen in the binder portion. As shown in
FIG. 1B
, when the book
16
is opened above the glass plate
10
, the binder
18
of the book
16
will be above the glass plate at a certain height. The binder will possibly be out of the depth of field and cause the scanning image to be fuzzy and unreadable.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of correction and assembly of a scanning device.
According to the present invention after a correction adjustment of the scanning module, a glass plate of a scanning module is placed at a lowest tolerant point of MTF-DF curve in order to improve the range of the optical depth of field of the scanning device. Therefore, users can employ the maximum tolerant range of DF to scan a wrinkled document or the book as shown in
FIGS. 1A and 1B
.
REFERENCES:
patent: 5484994 (1996-01-01), Roustaei
patent: 5565668 (1996-10-01), Reddersen et al.
patent: 5581068 (1996-12-01), Shepard et al.
patent: 5703721 (1997-12-01), Bietry et al.
patent: 5811828 (1998-09-01), Laser
patent: 5847884 (1998-12-01), Kamon et al.
patent: 5945670 (1999-08-01), Rudeen
patent: 6056198 (2000-05-01), Rudeen et al.
Lu Albert
Tsai Jenn-Tsair
Kim Ahshik
Lowe Hauptman & Gilman & Berner LLP
Mustek Systems Inc.
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