DD259327A3 - METHOD FOR DEFINED ILLUMINATION OF THE PROJECTION SURFACE IN A DEHYDRATION UNIT - Google Patents

Abstract

Arrangement for the defined illumination of the projection surface in an equalizing device. In order to realize a defined desired course of color mixing and brightness distribution by means of a defined illumination, a plurality of different color filter layers each having a defined, locally dependent color density progression are arranged in the beam path in the equalization device in the illumination beam path emanating from the light source.

Description

embodiment

The invention is explained below with reference to the drawings

 Show it:

Fig. 1: The beam path in an equalization device

Fig. 2-5: Examples of changes in the intensity profile by gradient filter combinations according to the invention Fig. 6-8: Production possibilities for spectral gradient filters to be used

In Fig. 1, a light source 1 emits a light beam 2 in which successively an optical active means 3, a Fresnel condenser 4, an image carrier 5 with an image 6, a projection lens 7 and a projection table 8 are arranged with a photosensitive layer 9. All these components are aligned to the optical 0-0 of the projection lens 7, which is also the optical axis of the equalizer. The image carrier 5 and the projection table 8 are each mounted at two angles to the optical axis 0-0 perpendicular axes and pivotally. In each case one of the two axes X-X is parallel and the other Y-Y is directed at right angles to the plane of the drawing. The mutual association of the image carrier 5, the projection lens 7 and the projection table 8 is given by the Scheimpflug condition and the lens equation. The projection lens 7 projects the image 6 illuminated by the light source 1 onto the photosensitive layer 9.

In the following education and arrangement of the removable from the illumination beam path 2 optically active means 3 are explained in more detail in some examples. The invention relates to the two basic color exposure methods used in equalization:

In the additive process, the desired color spectrum from the three primary colors red, green and blue is achieved by successive (added), temporally different exposure.

In the subtractive process, the color mixture desired for the exposure is achieved in an exposure process by filtering (subtracting) the unwanted color components from white light.

For the color components red, green, blue used in the color exposure process, the respective intensity profile of the illumination on the projection table 8 is first measured as I = f (R). For this purpose, a scan in the plane of the table surface at sufficiently many individual points by means of a photoelectric receiver. From this, the corresponding intensity profile is determined by computational transformation, taking into account all the optical elements located between the table and filter plane, which influence the light distribution and intensity, in the plane of the color filters as I _F = f (r). The color density D = f (r) is determined from

D = log

 Should

FIG. 2 shows a first embodiment of the arrangement according to the invention. Two colors (here red and green) are reduced to the color with the absolute intensity minimum (here blue). By pre-switching a neutral gray gradient filter the desired desired course S is achieved. The shape of the white setpoint curve depends on the intended application (positive, negative, contrast-compensated image templates).

In the embodiment shown in FIG. 3, each color is reduced by itself to the predetermined target profile by means of a gradient filter. In this case, the neutral gray gradient filter is eliminated, since the area covered jointly by all the color curves corresponds to the effect of this filter in FIG.

Fig. 4 shows an embodiment which is applicable only to the additive method. It is based on the color with the absolute intensity minimum and for these a neutral gray gradient filter to achieve a predetermined desired course S determined (here blue). The two other colors (here red and green) are only reduced to a higher intensity curve that is proportional to the minimum intensity curve. Different exposure times using the additive method (3-fold exposure with the respective color) for the individual color separations take into account the different curve levels of the individual color components. This achieves a short overall exposure time for additive processes. With simultaneous action of the three Farbkompohenten, ie in application of the subtractive method, there is no balance of color components, and thereby no white light is achieved. The color combination consists of a gradient filter for red reduction, a gradient filter for reduction green and a neutral gray gradient filter for the reduction of blue to the target curve. The neutral gradient filter also works on the reduced curves red and green at the same time. This results in a red and green not shown Sollverlauf for all three colors.

The variant shown in Fig. 5 is applicable only for the additive method. By means of appropriate color filters, all three color components are reduced to an associated Sollverlaufkuve which is set as high as possible. The three desired course curves are proportional to each other.

4, now, e.g. produced by different exposure times, any color mixtures. The brightness reductions in the individual color components can be z. B. make with the usual in the subtractive process color filter substances. For example, red can be reduced to blue-green, green to purple, and blue to yellow. For equalization devices in which after the additive process, the color filters corresponding to three color components are respectively pivoted into the vicinity of the diaphragm plane of the objective, it is possible, when the filter plane is sufficiently far away from the entrance pupil of the objective, to compensate for the illumination of the objective Image carrier or the projection surface by applying a neutral gray leveling layer on the color filters to achieve. This layer is to be dimensioned in accordance with the brightness distribution present in the individual color, taking the soil distribution into account. In the case of possible different positions of the light source in the additive method, a correspondingly changed dimensioning of the graduated filter is to be carried out.

In the following, details of possible production variants of the color gradient filters used according to the invention will be discussed in greater detail.

In Fig. 6 are provided on a glass substrate 10 annular films 11 with different thickness and width, which are combined with each other depending on the given density profile.

There is also the possibility to combine all individual filters used by combining in a device, for. B. by using the three layers of a suitable color film. In Fig. 7, the differential exposure of a circular rotating film 13 is shown, on which a fixed, a slot having aperture 13 is arranged. About another, movable aperture 14 are transmitted to the film annulus for annulus, the colors red, blue and green. The desired density changes are achieved by changing the brightness, the speed change of the film or variation of the contour of the wedge slot for each color. In addition to this differential film exposure variant, it is also possible to make the color irradiation on the entire film surface and to achieve a defined density profile on the film by varying the contour of an exposure opening on the fixed diaphragm or the emission characteristic of the light source. By white; In any of these methods, any density distributions of the filters, including the rotationally symmetric ones described above, can be achieved. By way of example, the filter material may consist of a transparent casting mold 14 of cast-colored gelatin 15 (FIG.

Finally, a suitably usable color film can also be produced by exposure to the illumination device of the equalization device itself. Since the density variations of the illuminator per color are transferred to the ink film upon exposure, the negative or positive of the film is usable as a corresponding filter. The exposure takes place at the point where the filter to be made wirsam.

Claims (4)

1. Arrangement for the defined illumination of the projection surface in an equalization device in which optically active means are arranged in the light beam path emanating from the light source, characterized in that a plurality of different color filter layers with respectively spatially dependent Farbdichteverlauf arranged in the beam path sine as optically active means. 2. Arrangement according to claim 1, characterized in that the color filter layers are the color layers of a color film. 3. Arrangement according to claim 1 or 2, characterized in that at least one neutral filter is provided with a defined Schwärzungsveriauf in the beam path. 4. Arrangement according to claim 1, characterized in that the color filter layers are formed separately from one another inserted into the beam path. For this 3 pages drawings Field of application of the invention The invention relates to an arrangement for the defined illumination of the projection surface in an equalization device, in which optically active means are arranged in the illumination beam path emanating from the light source. Characteristic of the known technical solutions On optical equalization devices, with which color photographs are enlarged and equalized, high demands are placed on a uniform illumination of the image carrier surface or the projection surface with respect to all color components of the light of the light source. This requirement applies both to work according to the additive method and to the subtractive method. It is already known to aim for compensation in the illumination of the individual surface elements of image carrier or projection table in an optical equalization device by means of different, neutral gray graduated filters and / or tiltable lenses (WP 143656). The said means are arranged in the illumination beam path. However, they act equally on all color components of the "white light" of the light source used, so that caused by the device color errors (deviation from "white") may occur, which can not be corrected with respect to the projection plane. In the case of optical equalization devices which contain optical components in the illumination beam path which cause chromatic aberration, such as Fresnel condensers and redistribution lenses made of plastic materials, different brightness profiles can occur in the surface of the image carrier and the projection plane for the different color components. Although these differences can be limited by different position of the lamp on the optical axis assigned to the respective color component, this possibility does not exist with the subtractive method, since the illumination is assumed to be "white light" "White" lighting is also required when working with black and white materials and when visually viewing the projection image. · Object of the invention The aim of the invention is to avoid the deficiencies of the described prior art on the projection surface of the equalization device for both the additive and the subtractive method. Explanation of the essence of the invention The object of the invention is to realize a predetermined desired course of color mixing and brightness distribution by means of defined illumination. The object is achieved in an arrangement for the defined illumination of the projection in an equalization device, are arranged in the emanating from the light source illumination beam path optically active means, characterized in that a plurality of different color filter layers are arranged with each location-dependent Farbdichteverlauf in the beam path as an optically active means. Advantageous embodiments are that the color filter layers are the color layers of a color film, in the beam path at least one neutral filter is provided with a defined blackening or in the separately manageable training of the color filter layers to a time-shifted introduction into the beam path with a common optical effect by superimposing enable.