Gear cutting – milling – or planing – Milling – Process
Reexamination Certificate
2000-06-29
2003-07-01
Wellington, A. L. (Department: 3722)
Gear cutting, milling, or planing
Milling
Process
C409S132000, C409S305000, C409S309000, C409S315000, C409S348000
Reexamination Certificate
active
06585461
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of working a diffraction optical grating element used in an image output unit, particularly a color image output unit, in an image forming apparatus, e.g., a copying machine and a printer.
The present invention also relates to a method of working a mold for molding an optical element such as a diffraction grating element.
The present invention also relates to a method of forming a groove in an optical element, particularly a diffraction grating element shape.
BACKGROUND OF THE INVENTION
An example of use of a diffraction grating element in an apparatus which line-scans a subject such as an original and reads and obtains the color image information of the subject with an image sensing element array is disclosed in, e.g., U.S. Pat. No. 5,838,480.
According to this reference, an image information beam from the subject is guided onto an image-forming substrate through an optical system on the first optical path and the first and second lens elements on the second optical path.
The first lens element has a diffraction grating element shape.
With this arrangement, the image information beam can be split into a plurality of beams having different wavelength ranges, and the plurality of beams can correctly form an image on the image-forming substrate without color misregistration.
Japanese Patent Laid-Open No. 8-336701 proposes a method of working a curved surface having an arbitrary shape with high surface precision.
FIG. 12
shows an optical scanning unit in a color image forming apparatus incorporating an optical element according to the present invention.
Referring to
FIG. 12
, reference numeral
1
denotes a light source means such as a semiconductor laser;
2
, a collimator lens;
4
, an aperture diaphragm; and
6
, a cylindrical lens having a predetermined refracting power in only a subscanning direction to cause a beam passing through the aperture diaphragm
4
to form a linear image on the reflecting surface of an optical deflector
8
(to be described later) within a subscanning section.
Reference numeral
8
denotes a polygon mirror serving as the optical deflector and rotatably controlled by a driving means (not shown).
Reference numeral
10
denotes a scanning optical element with f&THgr; characteristics and having a refracting portion and a diffracting portion. A refracting portion
10
A is a toric lens having different powers in the main scanning direction and subscanning direction. A diffracting portion
10
B is comprised of an elongated diffraction optical grating element having different powers in the main scanning direction and subscanning direction.
Reference numeral
12
denotes a photosensitive drum.
Working of the optical element according to the present invention concerns the elongated diffraction optical grating element.
When seen from above, the diffraction grating used in the color image reading apparatus described above forms a combination of substantial elliptic shapes in the major- and minor-axes directions, as shown in FIG.
1
.
The diffraction grating used in this example forms a plurality of concentric ellipses having fine grooves, as shown in
FIGS. 3
to
5
with a section taken along the line A—A through the center in the minor-axis direction and a section taken along the line B—B through the center in the major-axis direction.
The color image reading diffraction grating is formed on the flat surface of a rectangular parallelepiped metal substrate
1
shown in
FIG. 2
by using this member
1
, formed long in the major-axis direction, as the mold.
FIG. 4
shows a ridge line of the grooves near the center in the A—A direction.
FIG. 5
shows a ridge line of the grooves near the center in the B—B direction.
The numerical values of the respective portions of the diffraction grating of this example are as follows.
The width of the rectangular parallelepiped 1: 9.648 mm
The length of the rectangular parallelepiped 1: 225.12mm
The material of the rectangular parallelepiped: phosphor bronze
A gap P among grooves: 0.729727 mm to 0.009882 mm
A height h
1
of the inclined portions of the grooves: 0.001488 mm
A height h
2
of the inclined portions of the grooves: 0.001488 mm
An inclination angle &agr;
1
of the grooves: 0.1168 degree
An inclination angle &agr;
2
of the grooves: 8.56 degree
Also, the number of grooves is 2,577.
Grooves must be formed in above number and with the above groove sizes within an area having a width W of 9.648 mm and a length of 225.12 mm of the rectangular parallelepiped.
Referring to
FIG. 1
, the grooves of the diffraction grating have substantially elliptic portions M in which the elliptic shapes formed by the grooves are completely closed, and substantially elliptic portions N
1
, . . . , and Nn in which the elliptic shapes formed by the grooves are not closed.
When the diffraction grating element shape described above is to be worked, the blade is moved on the workpiece in the X-, Y-, and Z-axis directions along the curves of the diffraction grating. Not only the blade is moved in the X-, Y-, and Z-axis directions, but is operated biaxially to match predetermined angles with respect to the X-, Y-, and Z-axes of the workpiece, thereby performing working.
The blade must be moved in the X-, Y-, and Z-axes of the workpiece, and its posture must be controlled biaxially.
To form a diffraction optical grating element shape on the upper working target surface of a workpiece W, as shown in
FIG. 6
, a curved surface R
1
at the central portion of the diffraction grating element shape is formed on the upper surface of the workpiece W, and after that a second groove portion R
2
is formed at the outer peripheral position of the curved surface R
1
of the central portion. Second and third groove shapes are sequentially formed by cutting.
The concave curved surface at the central portion is formed in the following manner. As shown in
FIG. 3
, the edge of the blade is moved with a predetermined feed pitch in the X-axis direction to form moving traces K
1
, K
2
, K
3
, . . . shown in
FIG. 3
with respect to the flat X-, Y-, and Z-axis coordinate planes on the working target surface of the workpiece W. In the Z-axis direction, the blade is controlled such that its cutting edge follows the shape of the curved surface of the central portion.
In this case, as shown in
FIG. 6
, part of the blade which forms a curved surface G
1
at the central portion interferes with the worked curved surface, and a contact mark with the blade portion is formed on the worked curved surface. This impairs the optical diffraction function.
SUMMARY OF THE INVENTION
In order to solve the problems arising when working the diffraction grating element shape described above, according to the present invention, there is provided a method of working a diffraction optical grating element shape on a working target surface, characterized in that a main spindle for rotatably supporting a cutting blade is provided on X-, Y-, and Z-coordinate axes of the working target surface, and an angle of an edge of the cutting blade mounted on the main spindle performs working to have an inclination with such an angle that interference with a planned working position at an outer peripheral portion of a curved surface of the diffraction optical grating element is avoided.
According to the present invention, there is also provided a method of working a mold for molding a diffraction optical grating element shape, characterized in that a main spindle for rotatably supporting a cutting blade is provided on X-, Y-, and Z-coordinate axes of a working target surface of the mold, and an angle of an edge of the cutting blade mounted on the main spindle performs working to have an inclination with such an angle that interference with a planned working position at an outer peripheral portion of a curved surface of the diffraction optical grating element is avoided.
Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention wh
Cadugan Erica E
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Wellington A. L.
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