Photocopying – Projection printing and copying cameras – Identifying – composing – or selecting
Reexamination Certificate
2000-01-28
2002-05-21
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Identifying, composing, or selecting
C355S038000, C355S040000
Reexamination Certificate
active
06392739
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to European Patent Application No. 99 101 595.9 filed in Europe on Jan. 29, 1999 and European Patent Application No. 00 100 242.7 filed in Europe on Jan. 18, 2000; the entire content of which is hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to a method for the optimization of a copying light profile of a photographic copier. The present application especially relates to the optimization of a copying light profile in a copier, which includes a local transmission modulator, for example a liquid crystal matrix. The invention further relates to the use of such a local transmission modulator in a photographic copier for the achievement of optimization.
BACKGROUND ART
Copier apparatuses for the copying of photographic originals, especially transparent originals, for example films (positive films, negative films), are known, for example, from DE 4308864, DE 4040498, or DE 19703063. The copier apparatuses described therein use an LC matrix (liquid crystal matrix) in order to influence the copying light used for the exposure process. The LC matrix serves the brightening or darkening of certain regions of the copy in order to so manipulate the copy of a photographic original in a desired manner. The mask used therefor according to which an LC matrix is controlled is derived from the photographic original and is therefore dependent on its respective image data.
Optical components such as a high-value illumination means and optical, light guide means, for example, mirrors, elliptical mirrors, lenses, stops, filters, light mixers, shutters and so on are used in a copier apparatus in order to achieve as smooth a profile as possible of the copying light (which means the copying light intensity or the copying light density) which is as free from variations as possible in order to thereby illuminate the original as optimally as possible.
However, in practice, the copying light profile achieved is not optimal. This can be caused, for example, by a less than optimal cooperation of the light conducting means or by undesired modifications of the copying light by the light conducting means. For example, annular structures can occur.
SUMMARY OF THE INVENTION
The inventors of the present application have realized that a local transmission modulator, for example an LC matrix or a controllable scatter matrix, can be used during a respective copier process not only for the manipulation of a copy in dependence of a given original, but also for the general improvement of the copying properties of a specific copier, and independent from the original to be respectively copied.
It is an object of the invention to provide a method and apparatus by which the copying light profile in a copy apparatus can be optimized. Furthermore, in accordance with the invention a local transmission modulator is used for this optimization.
Advantageously, a cost-effective optimization of the copying light profile is possible by using a local transmission modulator already present in a copier apparatus. The costly optimization process for then calibration of the optical components can then be simplified. It is further made possible to use cheaper optical components with larger manufacturing tolerances, since inhomogentities caused thereby can be equalized with the method in accordance with invention.
The method in accordance with invention is used in a photographic copier as described, for example, in European application number 99101595.9 and corresponding application s in USA, Japan, Canada and China, the disclosure of which is here by incorporated into the application. Such a copier apparatus uses at least one light source, for example a halogen lamp or LED diodes to produce the copying light. The produced copying light is guided in the copier apparatus through a number of optical, light conducting means, for example, shutters, lenses, mirrors, partially transparent mirrors, beam splatters, lenses, diffuses, prisms, and so on, along a beam path (optical axis) through the photographic original to the copier material. The light is preferably homogenized by homogenizing means, for example scatter disks, before it reaches the photographic original. The photographic original is transparent and can be, for example, a negative film or a positive film. The copier material is, for example, a photographic paper. The photographic original is shone through and the shone through original image is projected onto the copier material.
The copying light profile is then considered optimal when it takes on a desired form. Preferably, the copying light profile is formed in such a way (in the plane of the copy) that the copy of a photographic original results in a homogeneous copy (for example, homogeneously gray) when the photographic original is based on the photographic recording (for example by way of a camera) of a homogeneous (for example, homogeneously gray) image. If the photographic recording were perfect, the photographic original would then also be homogeneous and one would therefore desire a homogeneous copying light profile. However, the recording lenses of cameras cause a decrease of the exposure light strength from the center to the edge. Therefore, a copying light profile is then preferably considered optimal, when it at least partly equalizes this decrease and not only attenuates disruptions of the copying light caused by the light conducting means. A homogeneous picture recorded by a camera is thereby duplicated by an at least approximately homogeneous copy.
A local transmission modulator is preferably positioned in a photographic copier apparatus in the vicinity of the original and either therebefore or thereafter. The copying light is passed through the local transmission modulator. The local transmission modulator can change its transmission whereby it is preferably electrically controlled therefor. The change of the transmission preferably takes place spacially broken down (locally), which means different transmissions can be adjusted at different locations (elements of the transmission modulator). As already described in connection with the prior art, a specific transmission profile is adjusted at the transmission modulator in order to manipulate the brightness profile of the copy depending on the image data of the original for the copying of a photographic original. This transmission profile is in the following referred to as transmission profile preselected for the copying process. If no manipulation of the copy is planned, an even transmission profile is preselected according to the prior art. This was then the case in the prior art, for example, when the photographic original was a homogeneous picture.
According to the process in accordance with invention, the transmission profile of the local transmission modulator preselected for the copy process is changed in dependence of a given (actual) and a desired (nominal) copying light profile. The copying light profile can be described, for example, as the profile of a copying light intensity or an optical density of the copying light or the illumination intensity of the copying light or as the function of these variables. The transmission profile during the copying of an original which is supposed to represent a homogeneous picture is changed in such a way that inhomogeneities in the copy are removed or at least attenuated.
To change a transmission profile in such a way that the copying light profile is optimized, several steps are required. First, the given copying light profile in a copier apparatus must be measured. This copying light profile is dependent of the optical components used (light source; light conducting means; light scattering means, such as LC matrix, scatter disks; means light absorbing means, such as filters or also LC matrix) and depending on the type of the copier apparatus can even vary from copier to copier of the same type. The copying light profile broken down per area describes the strength of the copying light transverse to the light path
Kraft Walter
Nussbaumer Max
Adams Russell
Gretag Imaging Trading AG
Nguyen Henry Hung
LandOfFree
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