Photocopying – Projection printing and copying cameras – Illumination systems or details
Reexamination Certificate
1999-08-20
2002-01-22
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Illumination systems or details
C355S071000, C349S149000, C349S152000
Reexamination Certificate
active
06341008
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of photo finishing and, more precisely, a photographic copier which is also referred to as photographic printer or optical printer. Such a photographic copier serves the production of photographic prints in a photographic copier, films which, for example, were exposed in a photographic camera are projected onto photographic copier material (for example, photo paper).
BACKGROUND ART
The exposure of the copier material not always results in a satisfactory reproduction of the picture information captured on the film. An essential cause therefore is that the dynamic of the luminescence (Grayscaling) contained in the picture information to be depicted cannot be converted on the picture median. This is caused, for example, by the strongly reduced luminescence dynamic range of the photo paper compared to a photographic film. Furthermore, the sensitivities of the photo paper are dependent on the light used for the projection. All this must be taken into consideration for producing a photographic copy, for example, on photographic paper, in order to achieve a realistic reproduction on the photographic paper of the picture information captured with the film.
It is especially required for the achievement of a good copy quality that the brightness profile of the copy is manipulated. One reason herefore, for example, resides in that the brightness differences which are still recognizable by an observer of the original photographic picture information which forms the basis of the film (the original), are no longer recognizable for the observer of the photographic copy when these brightness differences are located in a dark or very bright region of the photographic copy.
In order overcome this disadvantage, photographic copiers or optical printers have been suggested which use a LCD matrix in the path of the exposure beam. The transparence of the individual elements of the LCD matrix and thus the intensity profile of the light incident on the photographic paper is controllable and the brightness profile can thereby be influenced.
Conventionally, LCD matrixes are used herefore which are also used in screens or displays. These LCD matrixes have a high number of elements and operate according to the polymerization principle. This means a polarization filter is switched in series before or after matrix and the polarization condition of the matrix can be changed by applying a voltage so that the polarizations condition is perpendicular or parallel to the polarization filter. A complete darkening by way of the matrix can be achieved therewith. Such a matrix is known from DE 28 20 965 and DE 40 40 498.
It is known from DE 43 08 864 to combine several closely adjacent elements to a group whereby one part of the element of the group are switched to bright and the other part of the group to dark. Depending on the ratio of the bright and dark elements, different Grayscales can be achieved.
The matrix described in DE 197 03 063 includes 1500 individually controllable Grayscale able points.
As already mentioned above, polarization effects are normally used for the LCD matrixes. A further example therefore is described in U.S. Pat. No. 3,926,520.
A disadvantage of the copier apparatus used in the conventional matrixes is the low degree of transmission of the matrixes. Because of the polarization filter alone, at least 50% of the light intensity are lost. In practice, the maximum transparency of the conventional LCD matrixes is less than 20%. This however means that the intensity of the illuminating means is used in the copier apparatus must be increased by at least a factor of 5 in order to compensate for the intensity loss because of the LCD matrix. The higher light power, however, causes a higher thermal load on the component of the copier apparatus and especially also the LCD matrix which absorbs a major portion of the light energy.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a photographic copier apparatus, wherein the influencing of the brightness profile is possible by way of a matrix without the requirement that the intensity of the illuminating means must be significantly increased.
This object is achieved with the features of the independent claims. Preferred embodiments are apparent from the dependent claims.
The photographic copier apparatus according to the invention includes, of course, a light source which emits the light required for the exposure of the photographic original. Typically, lamps, such as halogen lamps, are used as light source. However, in accordance with the invention, laser diodes or light emitting diodes can also be used which further reduce the thermal load.
In accordance with the invention, light sources of different colour, for example, lamps, or light emitting diodes of different colour can be used which light can be additively superimposed.
For example, a blue, green and red lamp can be provided which are mixed, for example, by way of a system for the optical mixing of the green, blue and red light. An optical mixing system can consists, for example, of mirrors which are, transparent for two of the three colors and reflect the other one of the three colors. An example for such a mixing system is disclosed in DE 43 09 795 C2. When differently coloured light sources are used, the spectrum of the exposure light for exposure of the copier material can be changed and adapted to the respective situation by changing the intensity of the different light sources or changing the time during which the differently coloured light sources act on the copier material. The respective situation is influenced, for example, by the type of the original material or copier material used, or by the image information contained in the original. Based on data on the copier material, the original material and/or the image information contained in the film, the duration and/or intensity with which the light of a specific colour acts on the copier material can be controlled by way of a data processing arrangement in order to so achieve an optimal picture quality. Alternatively or in addition to the differently coloured light sources, colour filters can be provided as described further below. These colour filters can also be controlled on the basis of the above-mentioned data in order to so influence the spectrum of the light acting on the copier material with respect to duration and intensity of the individual colours.
The above mentioned coloured lamps, i.e. the blue, green and red lamp can be realized by way of a lamp which emits white light and which is combined with a colour filter which only lets red, green or blue light pass.
To guide the light from the light source to the photographic original, to shine it therethrough and to guide it to the light sensitive copier material, optical, light guiding, for example, light bundling or light scattering means, such as lenses, mirrors, shudders, partially transparent mirrors, compound lenses, collecting lenses, dispersing lenses, prisms and so on are provided.
In order to produce a desired brightness profile on the light-sensitive copier material, a liquid crystal matrix is provided in the light path which is shone through by the light before it impinges on the photographic copier material. The individual elements of the liquid crystal matrix may be controlled so that the transmission of the individual elements can be changed. A light intensity profile is thereby produced so that individual regions of the photographic copier material can be more strongly exposed than others. The brightness profile of the photographic copier material can thereby be manipulated in the desired manner in order to produce an optimal picture for the observer on the copier material.
The brightness profile is manipulated depending on the image information captured by the film. For example, regions which would become dark on the copier material without manipulation are brightened when thereby contrast or brightness scales become more clearly apparent in the dark region. In order to be a
Adams Russell
Fuller R.
Gretag Imaging AG
Pennie & Edmonds LLP
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