Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1998-09-30
2002-01-15
Grant, II, Jerome (Department: 2624)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C250S555000, C359S813000
Reexamination Certificate
active
06339482
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a control method of switching multiple lens of a document image scanner, and particularly to a closed-loop control method which ensures the scanned image to be focused correctly by controlling each lens of different magnification positioning accurately to its correct position.
In the current design of image scanners, in addition to the commonly used single lens systems for scanning documents within a specific size, there are further multiple lens systems for scanning various types of documents of different sizes. Some new designs concerning multiple lens system, which will be described hereinafter, are all emphasized on the improvements to the positioning mechanism of lens or to the actuating mechanism of reflector. The objectives of the mechanisms are to ensure all the scanned images from the different size of documents can be precisely transmitted to the charge couple device (CCD) element through the lens or reflector switched or moved to the correct position, and therefore, a good quality of scanning can be achieved.
FIG. 1
is a multiple lens switching mechanism of the prior art. The mechanism utilizes a motor
12
and reduction gears
14
to switch a set of lenses
18
mounted on a sliding rack
16
to some specific positions aligning to an opto-electric module, and thus providing various image resolutions.
FIG. 2
is another prior art scanner with dual-lens mechanism. A lever mechanism
22
moves a dual-lens base
24
sliding on a rail
26
to change the lenses and image resolutions.
FIG. 3
is further a scanner of prior arts with dual-lens and a movable reflector mechanism. The images of two different kinds of documents
34
and
36
are taken by two lenses
38
individually and reflected by a reflector
32
selectively moving into one of the two optical paths for transmitting the image into the opto-electric module.
In summary, the multiple lens systems of prior arts are emphasized not on the control method but on the positioning or moving mechanisms of the lens. In other words, the control methods of prior arts for positioning the lens are generally of mechanical manners. The common methods are using stoppers or position detectors for the lens to stop at their predetermined position after moving. But this “open-loop” control method relies on precise fabrication of mechanical components; otherwise, the mispositioning of the lens will occur. Basically, a mechanical “open-loop” control method cannot ensure a reliable positioning.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide a “close-loop” control method for precisely positioning the lens of a multiple lens system of scanner to accurate positions during the switching control.
The present invention provides a control method for positioning multiple lens of a scanner to their accurate position. The method mainly uses a linear reference image, such as a calibration paper with some marks in the linear scanning range, taken by a specific lens to the CCD for deciding if the lens is well positioned. The decision is made by one of the following three methods:
1. Absolute Position Method
Make a mark on a calibration paper for the scanner. Take previously the image position of the mark that is imaged on a certain pixel of the CCD as a standard pixel N
l
through a specific lens reaching its correct position. Thereafter, the specific lens is controlled to move toward the correct position and the mark imaged on the pixels of the CCD is continuously monitored as an instant pixel n
l
during the switching of the lens. In comparison, if the instant pixel is not the same as the standard pixel, the lens will be kept moving until the lens reaches the correct position.
2. Relative Position Method
Make two marks relative to two reference points on a calibration paper for the scanner. Take previously the image positions of the marks and two reference points that are imaged on four certain pixels of the CCD and record as standard differential values N
f
and N
r
of the two mark pixels relative to the reference point pixels respectively through a specific lens reaching its correct position. After then, the specific lens is controlled to move toward the correct position and the two differential values n
f
and n
r
are continuously monitored during the switching of the lens. In comparison, if the values N
f
, N
r
and n
f
, n
r
are not the same respectively, the lens will be kept moving until the lens reaches the correct position.
3. Range Method
Make two marks spaced with a distance L on a calibration paper for the scanner. Take previously the image positions of the marks that are imaged on two certain pixels of the CCD and record as a standard differential value N
l
of the two mark pixels through a specific lens reaching the correct position. After then the specific lens is controlled to move toward the correct position and the differential value n
l
is continuously monitored during the switching of the lens. In comparison, if the value N
l
and n
l
are not the same, the lens will be kept moving until the lens reaches the correct position.
As described above, the lens is controlled to move to the correct position by the continuous feedback signals from the CCD, so the accuracy and reliability of the positioning can be kept without being influenced from any worn-out of frequent movements of the mechanism.
The featuresad advantages of the present invention will be described or will become apparent from the following more detail description of preferred embodiments.
REFERENCES:
patent: 5841121 (1998-11-01), Koenck
Chang Te-Chih
Tsai Jenn-Tsair
Grant II Jerome
Lowe Hauptman & Gilman & Berner LLP
Mustek System Inc.
Worku Negussie
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