Optics: measuring and testing – Focal position of light source
Reexamination Certificate
1999-02-24
2003-07-22
Nguyen, Tu T. (Department: 2877)
Optics: measuring and testing
Focal position of light source
Reexamination Certificate
active
06597441
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for calibrating a reflective lens, and more particularly to an apparatus and method for calibrating a reflective lens for being used in manufacturing an image scanning apparatus.
BACKGROUND OF THE INVENTION
As one of the peripheral equipment of a personal computer, the image scanner has become quite popular among computer users. The manufacturers of image scanners devoted themselves to improving the shortcoming and function of each component. Among the components of an image scanner, a reflective lens set is used to direct the image light beam of a scanning spot to a mirror set, and to focus on a charge coupled device (CCD) for being sensed. The reflective lens set, the mirror set and the CCD are commonly arranged inside a carriage. Because of the deviation of the lens
11
in a reflective lens set (please refer to FIGS.
1
(
a
) and
1
(
b
) respectively showing the deviation caused by rotational displacements of the lens
11
and FIG.
1
(
c
) showing the deviation caused by a translational displacement of the lens
11
), it results in a shift or deflection of the actual scanning line constructed by the reflective light path. The various errors on the scanning lines due to the inappropriate placement of lenses in a reflective lens set are shown in FIGS.
2
(
a
)~
2
(
d
).
FIG.
2
(
a
) shows an error in the X-direction (where X-direction is parallel to the direction of the scanning line) due to the inappropriate placement of a lens in a reflective lens set. The error causes a change in the scanning scope (X-direction) which results in a part of a scanned document being beyond the scanning window so that the image of that part can not be obtained. It also results in that the distance between the left end of the scanning line and the CCD is different from the optical distance between the right end of the scanning line and the CCD. It further affects the depth of view and the resolution of a scanning image.
FIG.
2
(
b
) shows an error in the Y-direction (where Y-direction is parallel to the moving direction of the carriage) due to the inappropriate placement of a lens in a reflective lens set. The error causes a shift of the scanning spot in the Y-direction, resulting in a change in its optical distance. Moreover as the scanning spot shifts to the edge of or outside the transparent slot, a chromatic aberration phenomenon will be occurred to affect the scanning process.
FIG.
2
(
c
) shows an error in both X-direction and Y-direction due to the inappropriate placement of a lens in a reflective lens set. The error causes a shift of the scanning spot in the X and Y directions simultaneously resulting in a change in its optical distance and a distortion of the scanning image. The change in the optical distance further affects the depth of view and the resolution of the scanning image. FIG.
2
(
d
) shows an error in the light path due to the inappropriate placement of a lens in a reflective lens set. The deflected scanning line and the original scanning line will intersect at a right scanning position at a certain scanning height h
1
; however, a change in an optical distance and a chromatic aberration phenomenon may be occurred due to part of the light in the light path being blocked.
The above-mentioned deviation phenomenon is frequently appeared in the step of developing various parts of an image scanner during performing a verification process after mock-up or injection molding. It seriously affects the scanning quality and must be corrected by a calibrating apparatus and method after finding out the deviation factor Taiwanese Patent No. 325554 has disclosed a method for calibrating an assembling reflective lens of the linear scanning device. However, that calibrating method is relatively complicated. As the number of the reflective lenses in a reflective lens set increases, it requires the fabrication tools with higher precision for that calibrating method. Besides, the prior method performs an observation of the calibration at the location of a CCD and results in low accuracy because only a scale-down image is observed at the location of a CCD.
Thus, it is tried by the applicant to deal with the situation encountered with the prior art.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an apparatus and a method for calibrating the various errors of a reflective lens on a carriage for being used in manufacturing an image scanning apparatus.
According to one aspect of the present invention, the apparatus adapted to be used in manufacturing an image scanning apparatus for calibrating a reflective lens on a carriage includes a fixing unit for fixing thereon the carriage, three point light sources located at three lined-up positions respectively, for respectively emitting point light beams to transmit along corresponding one of predetermined light paths of the image scanning apparatus into the carriage and pass out of the carriage from one end thereof, and a calibrating device having thereon at a first distance from the end of the carriage a first set of three projective points from the three point light beams passing out of the end of the carriage and a first set of three calibrating points corresponding to the three point light sources and at a second distance from the end of the carriage a second set of three projective points from the three point light beams passing out of the end of the carriage and a second set of three calibrating points corresponding to the three point light sources for matching each of the projective points on the calibrating device with a corresponding one of the calibrating points by adjusting an angle and a position of the reflective lens on the carriage so as to achieve a calibrating function.
In a preferred embodiment, the three lined-up positions are located over which an image sensing device of the image scanning apparatus is to travel.
In another preferred embodiment, the three lined-up positions are located to which the light paths of the image scanning apparatus are to extend. Preferably, the three point light sources are laser light sources.
Preferably, the calibrating device includes a first calibrating plate located at the first distance from the end of the carriage for obtaining thereon the first set of three projective points and the first set of three calibrating points and a second calibrating plate located at the second distance from the end of the carriage for obtaining thereon the second set of three projective points and the second set of three calibrating points.
Preferably, the first calibrating plate and the second calibrating plate are made of transparent material.
Preferably, the end of the carriage is provided for accommodating an object to be scanned.
In accordance with another aspect of the present invention, the method of calibrating a reflective lens on a carriage for being used in manufacturing an image scanning apparatus includes the steps of (a) fixing the carriage to a certain position, (b) installing three point light sources on three lined-up positions respectively, (c) at a first distance from one end of the carriage defining a first set of three calibrating points with respect to the three point light sources, (d) at a second distance from the end of the carriage, defining a second set of three calibrating points with respect to the three point light sources, (e) causing each of the three point light sources to transmit along corresponding one of predetermined light paths of the image scanning apparatus into the carriage and passing out from the end of the carriage so as to obtain a first set of three projective points and a second set of three projective points, and (f) adjusting an angle and a position of the reflective lens on the carriage for matching each of the projective points with a corresponding one of the calibrating points so as to achieve a calibrating function.
In a preferred embodiment, the first set of three projective points and the first set of three calibrating points are disposed on a first
Tsai Jenn-Tsair
Tsaur Chieng-Ming
Katten Muchin Zavis & Rosenman
Mustek Systems Inc.
Nguyen Tu T.
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