Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-05-22
2002-02-19
Rogers, Scott (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S406000, C358S296000
Reexamination Certificate
active
06348979
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to engraving heads of the general type disclosed in Buechler U.S. Pat. No. 4,450,486. Such engraving heads comprise a diamond stylus carried by a holder mounted on an arm projecting from a torsionally oscillated shaft. A sine wave driving signal is applied to a pair of opposed electromagnets to rotate the shaft through a maximum arc of approximately 0.25° at a frequency in the neighborhood of about 3,000 to 5,000 Hz.
A guide shoe is mounted on the engraving head in a precisely known position relative to the oscillating stylus. The engraving head is supported for tilting movement by a set of leaf springs secured to a rearwardly projecting bar. A DC motor rotates the bar so as to bring the guide shoe into contact with a printing cylinder to be engraved. When the guide shoe is in contact with the printing cylinder, the stylus oscillates from a position just barely touching the printing cylinder to a retracted position about 100 microns distant from the surface of the cylinder.
Once the guide shoe is in contact against the printing cylinder a video signal is added to the sine wave driving signal for urging the oscillating stylus into contact with the printing cylinder thereby engraving a series of controlled depth cells in the surface thereof. The printing cylinder rotates in synchronism with the oscillating movement of the stylus while a lead screw arrangement produces axial movement of the engraving head so that the engraving head comes into engraving contact with the entire printing surface of the printing cylinder.
In engraving systems of the type taught by Buechler, it is necessary for the machine operator to perform a tedious trial and error setup procedure at one end of the printing cylinder prior to commencement of engraving. This procedure involves adjustment of the gain on amplifiers for the sine wave driving signal and the video signal so as to produce “black” printing cells of a desired depth together with connecting channels of another desired depth and clean non-engraved white cells or areas. Each change of one of the control variables interacts with the others, and therefore the setup becomes an iterative process.
There is also a need in the engraving industry to provide an engraving system and apparatus with imaging and focusing capabilities which further facilitate automatically focusing on a surface of the cylinder and subsequently capturing images and measuring engraved areas on the surface. What is also needed is an engraving system which can quickly measure a dimension of a cut or cell, for example, of precisely controlled dimensions during set-up or real-time operation of the engraver.
There is a further need to provide a system and method for processing data corresponding to captured images, for example, by eliminating undesired image data or filling in discontinuous data corresponding to gaps in the array of data which correspond to gaps in a captured image.
What is also needed is an engraver comprising an apparatus or method for scaling or calibrating the intensity of light used in the focusing process to enhance automatically focusing, measuring and engraving cuts of precisely controlled dimensions.
It has been found that electronic images of engraved areas on copper printing cylinders can be captured with a charge-coupled device (CCD) and digitally processed to obtain measurements of the engraved areas using various prior art techniques. Typically, images of engraved areas show up as isolated dark regions where the incident light has been defracted out of the optical system due to multiple reflections within the interior of the engraved area. However, the quality of the captured images can be degraded by various artifacts or image noise which can occur individually or in combination. Some of the sources of these artifacts are wear of the diamond stylus used to engrave the engraved areas, ambient light, and uneven or inconsistent illumination over the imaged region.
The diamond engraving stylus used to engrave areas is susceptible to wear and “chipage” during engraving which, in turn, alters the interior shape of the engraved areas. This can result in significant levels of optical energy being reflected back into the optical system rather than defracted out of the optical system. Such energy shows up as bright spots on top of the otherwise dark engraved cells, hereinafter referred to as “glare” and can result in inaccurate measurements of the engraved area. Ambient light (from room lighting reflecting off the copper surface and the engraved areas) can also contribute to this glare.
Inconsistent or uneven illumination of the engraved areas creates further image noise in the electronic images which can result in inconsistent measurements of the engraved areas. If the luminous intensity upon the copper surface is too bright, “blooming” can occur in the CCD, thereby resulting in electronic measurements or dimensions which are smaller than the actual measurements or dimensions of the engraved area. When the luminous intensity is too dark, the edges of the engraved areas blend into the background surface of the copper, which causes electronic measurements which are larger than the actual engraved measurements.
FIG. 20
illustrates one prior art technique for attempting to reduce some or all of the aforementioned problems encountered in the past. In particular, this technique employs a Xenon flash bulb
800
which, when energized, flashes light through a fiber optic bundle
804
through a linear polarizer
810
. After being polarized, the light travels though a collimating lens
812
where it contacts a 50-50 beamsplitter
814
and passes through objective lens
816
onto surface
802
a
of cylinder
802
. Thereafter, it is reflected back through objective lens
816
, through beamsplitter
814
, and captured by CCD array
808
a
of camera
808
. While the placement of a single polarizer in line with the light source before it is reflected onto surface
802
a
of cylinder
802
has facilitated overcoming some of the aforementioned problems, what is needed is an engraver, system and method having an improved image system for imaging of engraved areas and facilitating reducing problems of the past, including problems resulting from diamond wear, inconsistent illumination, “blooming”, glare and the like.
It is therefore seen that a need has existed for an engraving system having image means which may be quickly and easily set up to engrave cells of precisely controlled dimensions in the surface of a gravure printing cylinder.
SUMMARY OF THE INVENTION
In one aspect, this invention comprises a method for adjusting an engraver to engrave a cylinder with an actual cut according to predetermined setup parameters, said method comprising the steps of: (a) determining an error value corresponding to the difference between said predetermined setup parameters and an actual measurement of a portion of an engraved area on said cylinder; and (b) using said error value to adjust said engraver to engrave said actual cut in accordance with said predetermined setup parameters.
In another aspect, this invention comprises a method for measuring a portion of an engraved area on a cylinder in an engraver, said method comprising the step of generating a plurality of actual dimension values corresponding to said portion.
In still another aspect, this invention comprises a system for measuring a portion of an engraved area on a cylinder in an engraver, said system comprising a measuring device for generating a plurality of actual dimension values corresponding to said portion.
In yet another aspect, this invention comprises an error correction system for use in an engraver suitable for engraving a cylinder with an actual cut in accordance with predetermined setup parameters, said error correction system comprising determining means for determining an error value corresponding to the difference between the predetermined setup parameters and a measurement of the actual dimensions of a portion of an engraved area on said cylinder; and a syst
Flannery David
Seitz David R.
Staub Thomas P.
Thomas Matthew A.
Jacox Meckstroth & Jenkins
MDC Max Daetwyler AG
Rogers Scott
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