DE972204C - Method and device for regulating the exposure when copying color images - Google Patents

Description

ISSUED JUNE 4, 1959

A 21328IX157 a

The invention is based on a method for copying color images using of white copy light and of subtractive color filters that can be injected into the copy light beam path. The method according to the invention is based on the assumption that in many color photographs all color components are roughly the same and it is therefore advisable to use the entire image content of the color image both in terms of its color composition and in terms of its To sum up the density and preferably to add a neutral gray to this mixed value.

It is known to measure the color and density of the color negative with the help of photo cells and then the intensity of the copying light source according to the previous measurement rules. The color-sensitive paper is exposed after each measurement and Adjustment of the copy light source one after the other in three sequences with additive filters.

In other known color copiers, subtractive, overlapping color filters are used by Hand pushed more or less deep into the illumination beam path and thereby changed the color composition of the copying light. the However, the optimal setting of the color filter must be determined empirically, so that it becomes necessary to make sample copies. It has also already been proposed when

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Copying of color negatives to compensate for color distortions in such a way that after an exposure post-exposures of the copy material by white copy light using subtractive color filters can be made. Here, too, the color filters are introduced by hand; the selection of the filters used and the duration of the post-exposure must also be determined by ίο test copies before copying. For the division Tables are required for the total exposure time in exposures with and without a filter.

To overcome these disadvantages, it is proposed according to the invention, when copying Color images using white copy light and into the copy light beam path Switchable subtractive color filters the effect of the copying light separately according to the proportions of the individual, basic colors to be controlled photoelectrically, with the effect of the individual color components of the copying light on the copying material by switching on the complementary subtractive color filter is canceled as soon as a predetermined amount of copy light of the respective Color has hit the copy material.

To carry out the method according to the invention, a device can be used in which the Color filters are assigned photoelectric control devices, whose photocells each for one are sensitive to a certain spectral range; each control device activates the associated one Color filter into the beam path of the copier light source as soon as a predetermined copier

light of the corresponding spectral range has hit the associated photocell

According to the invention, the photocells can either be between negative and lens or behind a partially transparent mirror between the lens and positive plane is arranged, or lie above or below the positive plane. In the latter In this case, the measurement is carried out through the light-sensitive paper. If the photocells are arranged near the positive plane, they are intended to carry the mixed and collected light of the receive the entire image via one or more reflectors. These reflectors can also be arranged laterally next to the magnifying frame.

The subtractive color filter or their holder can according to the invention the switch for Control the copy lamp in such a way that they intervene and lock into the engaged switch the incidence of the last subtractive color filter in the copy light beam path the switch to Enable interruption of lamp power.

In this way, the copying process is largely mechanized and simplified.

Some institutions for the exercise of the

driving are shown in the drawings, for example, namely shows

Fig. Ι the exposure beam path of an enlarger with the control device for the subtractive color filters, the photoelectric Cells are arranged below the positive plane,

2, 3, 4 and 4a further possibilities of arranging the photoelectric cells,

Fig. 5 shows an electrical circuit diagram and

6 and 7 the switch for the copy light source in different positions.

The white light emitting light source of the enlarger is with 1 and the condenser labeled 2, while the subtractive color filters are labeled 3, 4 and S. Of the The holder for the color negative is numbered 6, the lens is numbered 7 and the positive plane is denoted by Number 8.

In the device according to FIG. 1, a reflector 9 is provided below the positive plane 8, which reflector can also be replaced by a white surface. This reflector collects the colored light of the entire projected image onto three photoelectric cells 10, 11, 12. The photoelectric cells are either sensitized so that they only respond to certain spectral regions of the copying light, or they are preceded by filters in the additive primary colors. Each of the cells 10, 11 and 12 is connected to a capacitor which changes its state of charge under the influence of the photocurrent of the cell and, after reaching a predetermined voltage value, via a circuit arrangement which has a solenoid 13, 14 or 15 , causes the inclusion of the associated subtractive color filter 3, 4 or 5 in the copier light beam path. The circuit arrangements connected to the capacitors do not form the subject of the invention and are only shown schematically by the rectangle 16. I ₀₁ ,

The switch for turning on the copier light is denoted by 17 in FIGS. This has an _{opening i7 a} to accommodate the holder of the subtractive color filters 3, 4, 5 and also contacts 19, 20 for the solenoid 18 and contacts 1,05 2i, 22 for switching on the copy lamp 1. A spring 23 ensures that the pressure switch 17 automatically returns to its original position after actuation and after release.

In FIGS. 2 to 4a, further possibilities n _{0 of} the arrangement of the photoelectric cells 10, 11, 12 are shown. While the subtractive color filters 3, 4, 5 can be provided at any point of the illumination or exposure beam path, the photocells 10, 11, 12 responding to the three additive basic colors must be in the exposure beam path, i.e. between the negative and positive plane or below the Lying on the positive plane. In the embodiment according to FIG. 2, three groups of three photocells 10, 11, 12 in general are arranged behind each reflector 9, 9 ', 9 ". In the embodiment according to FIG. 3, the photocells 10, 11, 12 receive the copying light used for the measurement

via a semitransparent mirror 25 arranged in the copy light beam path, while in the embodiment according to FIGS. The cells mounted about ⁰ 120 staggered on the inner lateral surface of the truncated cone 26 are energized by the negative 24 by the radiant and scattered from the negative 24 of copying light.

In detail, the device works as follows: After the color negative 24 has been placed in the picture stage 6 and the photosensitive copying paper has been placed in the copier frame of the enlarger, the copier light source 1 is switched on by pressing the switch 17, thus initiating the exposure of the copier paper. The switch 17 is held in the switch position shown in FIG. 6 by the color filters 3, 4, 5, which _{engage in the breakout 17 a of} the switch 17 under the action of tension springs 28. When the copying light source ι is switched on, the photocells 10, 11, 12 are also hit by copying light beams at the same time, the photocurrents of the cells being dependent on the size of the proportion of the respective basic color in the measuring light. Once a predetermined, preferably controllable amount of printing light of a primary color is incident on the corresponding photoelectric cell, and thus the voltage of the associated Kon densators a predetermined value has been reached, the associated solenoid 13, 14 and 15 is energized via the connected circuitry which an associated with the Color filter 3, 4 or 5 attracts connected armature and thereby introduces the respective color filter into the copy light beam path. Is z. B. the predetermined amount of red copy light impinged on the photocell 12, the solenoid 13 is energized and the blue-green filter 3 is turned on. This ends the red exposure of the copy material «. In a corresponding manner, the yellow filter and the purple filter are switched on as soon as the predetermined amounts of blue and green copying light have hit the associated photocells. After switching on all three subtractive color filters 3, 4, 5, the exposure of the copy material is complete.

When switching on the third (last) color filter, the button 17 is released, the automatically returns to its original position under the action of the spring 23 (cf. FIG. 7). The copying light source 1 is switched off as a result of the interruption of the contact 21, 22. Further is caused by making contact of the contact elements 19, 20 that the solenoid 18 is excited is and the cooperating with a locking device hook 27 on the filter holders (e.g. on the filter halfcer 5 '). As a result, the filters 3, 4, 5 automatically move out of the beam path under the action of the springs 28 the copy light source removed again. The device is now ready for the next copy process ready for use.

Claims (6)

PATENT CLAIMS: 1. Method of copying color images using white copying light and of subtractive color filters which can be switched into the copy light beam path, characterized in that the action of the copy light is photoelectrically controlled separately according to the proportions of the individual primary colors, the effect of the individual color components of the copying light on the copying material is canceled by switching on the respective complementary subtractive color filter, as soon as a predetermined amount of copy light of the respective color component on the copy material is hit on. 2. Device for performing the method according to claim 1, characterized in that that the color filters (3, 4, 5) are assigned photoelectric control devices whose Photocells (10, 11, 12) each for a specific one Spectral range are sensitive, and that every control device is switched on of the associated color filter in the beam path of the copy light source as soon as a predetermined amount of copying light of the corresponding spectral range on the associated Photocell has hit. 3. Device according to claim 2, in particular enlarging device, characterized in that that the photocells (10, 11, 12) between the negative and positive plane are arranged. 4. A device according to claim 2, characterized in that the photocells (10, 11, 12) lie behind the positive plane (8) and receiving said mixed by a reflector (9) and collected light of the projected image i _O o catch (Figure . 1). 5 ·· Device according to claim 2 and 3, characterized characterized in that the photocells (10, 11, 12) are arranged around the positive plane and the colored light of the image is supplied via reflectors (Fig. 2). 6. Device according to one of claims 2 to 5, characterized in that the subtractive Color filters (3, 4, 5) or their holders locking into the engaged switch (17) for the copying light source intervene and this is switched off when the copying process is completed release the copy light source (1) (Fig. 6 and 7). Documents considered: German Patent No. 896 454; French patent specification No. 956641. 1 sheet of drawings © «09 578/284 7.56 (909524/15 5.59)