JPH04142529A - Light source device for photographic printer - Google Patents

Abstract

PURPOSE:To shorten a print exposure time and to improve the efficiency by selectively using a mirror box which reduce the quantity of insertion of a dimming filter into an optical path. CONSTITUTION:There are three kinds of mirror box, whose reflecting surfaces have three kinds of spectral reflection characteristic. When the kind and development conditions of color paper are changed or when a tungsten electric bulb 16 is replaced, the color balance of a light source needs to be adjusted and the quantities of insertion of three kinds of dimming filters are adjusted. When the color paper is changed in kind to paper which is large in the specific sensitivity of the red sensing layer, a cyan filter is inserted into the optical path greatly, but when a box 11 which has a spectral reflection characteristics high in short- wavelength side reflective index is used, the quantity of insertion of the filter is small and light quantity loss is also small. Then when the red light of the electric bulb 16 decreases in specific energy, a yellow and a magenta filter are inserted greatly into the optical path to keep total balance, but when a box 11 which has a spectral reflection characteristic high in long-wavelength side reflection factor is used, the quantity of insertion of the filters are small and the light quantity loss is small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light source device for a photographic printer, and more particularly to a light source device for a photographic printer that prints an image from a color film onto a color print photosensitive material.

[Prior art and problems to be solved by the invention] Conventionally, an original image recorded on a color film (negative film, reversal film) etc. is printed on a color print photosensitive material (
Photo printing devices (printers) that print onto color paper are known.

This printer includes a light source device, a control unit that controls the amount of exposure to color paper, and an optical system for imaging the color paper.

An example of a light source device will now be described with reference to FIG. 2. The light source device includes a tungsten bulb 16 as a light source that generates white light. A cold mirror 14 formed in a parabolic shape and having a reflective surface inside is attached to the tungsten light bulb 16. This tungsten bulb 16
On the exit side, there is a hollow rectangular cylinder having a reflective surface 10 formed on its entire inner surface, and a diffuser plate 1 attached to both ends of the cylinder.
A mirror box 11 including 2A and 12B is arranged. Between the tungsten light bulb 16 and the mirror box 11, there are dimming filters 18 each consisting of a Y (yellow) filter, an M (magenta) filter, and a C (cyan) filter formed to have uniform density, and YSM and C filters. A cut filter 20 is arranged.

Part of the direct light from the tungsten bulb 16 and the reflected light reflected by the cold mirror 14 is transmitted directly, and part of it is transmitted through the dimmer filter 18 and then through the diffuser plate 12A attached to one end of the mirror box 11. and enters the mirror box 11. The light incident on the mirror box 11 is reflected by the reflective surface 10 formed on the inner surface of the mirror box 11, and is emitted from the diffuser plate 12B at the other end. In this mirror box 11, the light is diffused and mixed in order to prevent color unevenness due to light that has passed through the light control filter 18 and light that has not passed through the light control filter 18. The light emitted from the diffuser plate 12B is transmitted to a film (
(not shown) is irradiated onto a color paper via a film and an imaging optical system to print an original image.

The specific energy spectral characteristics of a tungsten light bulb are, for example, as shown in FIG. 3, where the specific energy is low on the short wavelength side and high on the long wavelength side. For this reason, for example, in the case of color paper for color negative film, its spectral sensitivity characteristics are basically balanced by making the sensitivity of the blue-sensitive layer high and the sensitivity of the red-sensitive layer low, as shown in FIG.

Therefore, the luminous intensity of the three colors of light emitted from the light source device and the sensitivity of the three colors of color paper perfectly match, and when printing from a standard original plate, the three cut filters can be used without using a dimmer filter. enter the optical path at approximately the same time, the print exposure time will be the shortest.

However, in reality, this is rarely the case. For example, color papers have their own sensitivity characteristics depending on their manufacture and development, and are not always as shown in Figure 4. Furthermore, the spectral characteristics of a light source device also change depending on many factors. In other words, the color temperature and luminous intensity of tungsten bulbs vary, and the spectral reflection characteristics of their cold mirrors do not reflect part of the wavelength range necessary for printing, as shown in Figure 5, and also vary depending on the manufacturing batch. The spectral reflection characteristics are different. The spectral reflection characteristics of the mirrors in the mirror box are not flat over the entire required wavelength range, for example, as shown in FIG. 6(A), and this also varies depending on the manufacturing batch. Although the reflection by the cold mirror 14 occurs only once, the reflection by the mirror 10 in the mirror box occurs multiple times and is absorbed each time. The spectral characteristics of the reflected light gradually change.

Due to changes in each of these related factors, the luminous intensity of the three colors of the light source and the three color sensitivities of the color paper will no longer match, and even when printing from a standard original, one or two of the three cut filters will not match. The time required for each cut filter to enter the optical path is delayed.

This cut filter 20 is a guichroic filter, and its spectral transmission and reflection characteristics are as shown in the example in Fig. 7. As shown in the example in Figure 7, it does not transmit 100% of the wavelengths that you want to transmit, but reflects some of them. Due to the non-ideal spectral transmission and reflection characteristics of the cut filter that enters the optical path, the color balance of the print becomes somewhat distorted.

The dimmer filter 18 is used to change the balance of the three colors of the light source and eliminate the lag in the timing of entering the optical path of the three cut filters.With a standard original plate, the three cut filters enter the optical path at the same time. A part of the dimmer filter is inserted into the optical path in advance (so-called ``removing put heat''), adjusted, and then fixed.

However, since this dimmer filter is also a guichroic filter like the cut filter, its spectral transmission and reflection characteristics do not transmit 100% of the wavelengths that are desired to be transmitted, as shown in the example in Figure 7. As the amount of insertion increases, the loss of light amount increases.

This loss of light increases print exposure time and reduces efficiency. To prevent this, making tungsten bulbs more powerful or increasing the voltage will generate more heat, reduce stability, and shorten the bulb's lifespan.

An object of the present invention is to provide an efficient light source device that shortens print exposure time by minimizing the amount of light control filters inserted into the optical path.

[Means to solve the problem]

The present invention includes a light source that generates white light, a cylindrical mirror box having a reflective surface formed on its inner surface, and a cylindrical mirror box that is arranged between the light source and the mirror box to balance the color of the light that enters the mirror box. A dimmer filter to adjust,
The above problem was solved by preparing a plurality of mirror boxes each having different spectral reflection characteristics, and selecting and using the one that minimizes the amount of dimmer filter inserted into the optical path. .

[Effect]

When printing from a standard master plate, a photochromic filter is partially inserted into the optical path in order to adjust the color balance of the light source so that three cut filters enter the optical path at the same time and the exposure ends. However, as described above, the more the dimmer filter is inserted into the optical path, the more the loss of light amount increases and the longer the exposure time becomes.

Therefore, multiple mirror boxes with different spectral reflection characteristics,
For example, there are those that have high reflectance on average from short wavelengths to long wavelengths, those that have high reflectance on the long wavelength side compared to short wavelengths, and those that have high reflectance on the short wavelength side compared to long wavelengths. If various types are prepared and the one that allows the least amount of dimmer filter to be inserted into the optical path is selected and used, the exposure time will be the shortest without changing other conditions.

Previously, it was not possible to obtain mirrors with high reflectance on the long wavelength side compared to short wavelengths, but with recent advances in dielectric multilayer technology, it has become possible to obtain mirrors with high reflectance on the long wavelength side even with aluminum vapor-deposited mirrors. became.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings. Since the light source device of this embodiment has substantially the same configuration as that in FIG. 2, corresponding parts are given the same reference numerals and will be described in detail.

There are three types of mirror boxes 11 in this embodiment, and FIG. 1 shows three types of spectral reflection characteristic curves of the reflecting surface 10 of the mirror box 11. The reflective surface 10 is formed by coating the inner surface of the mirror box 11 with a dielectric multilayer film consisting of alternating layers of Ti0□, 5i02, etc. by vacuum deposition. In this example, a mirror box with the spectral reflection characteristics shown in FIG. 1(A), a mirror box with the spectral reflection characteristics shown in FIG. 1(B), and a mirror box with the spectral reflection characteristics shown in FIG. 1(C) are used. Three types of mirror boxes 11 are prepared. The spectral reflection characteristics of the reflective surface 10 shown in FIG. This is a characteristic in which the reflectance gradually decreases in the wavelength range. That is, it exhibits high spectral reflection characteristics on average from short wavelengths to long wavelengths. Figure 1 (B
) shows a high spectral reflection characteristic on the short wavelength side around approximately 400 nm, a nearly constant reflectance in the short to medium wavelength region, and a low reflectance in the medium and long wavelength regions. This is a characteristic in which the reflectance rapidly decreases from around 550 nm. That is, the spectral reflection characteristics are high at short wavelengths and low at long wavelengths. The spectral reflection characteristics shown in Figure 1 (C) show low reflection characteristics in the short wavelength region of about 440 to 450 nffl or less, and the reflectance gradually increases in the medium and long wavelength regions, and the maximum long wavelength side. This is a characteristic in which the maximum value of reflectance is approximately 96 to 97%. That is, the spectral reflection characteristics are low at short wavelengths and high at long wavelengths.

Here, it is necessary to adjust the color balance of the light source when the type of color paper and development conditions are changed or when the tungsten light bulb 16 is replaced. The adjustment involves adjusting the amount of insertion of the three dimmer filters 18 using a standard original plate in order to take the heat of the three cut filters 20. Three types of mirror boxes 11 prepared in advance are adjusted in order. It is preferable to select the mirror box 11 in which the amount of insertion of the light control filter 18 is the smallest when used in each case. For example, when the type of color paper is changed to one with a red-sensitive layer having a high specific sensitivity, many cyan filters must be inserted in the optical path to reduce the amount of red light. However, a loss in the amount of blue light and green light occurs depending on the amount of cyan filter inserted. Here, by using the mirror box 11 having the spectral reflection characteristics shown in FIG. 1(B) with high reflectance on the short wavelength side, only the amount of red light can be reduced, and the amount of insertion of the cyan filter can be reduced. Therefore, only a small amount of light loss is required for blue light and green light. next,
As the specific energy of red light becomes smaller, it is necessary to insert many yellow filters and magenta filters in the optical path to reduce the amount of blue light and green light other than red light to maintain the overall balance. Must be. However, depending on the insertion amount of the yellow filter and the magenta filter, a yellow filter causes a loss in the amount of green light and red light, and a magenta filter causes a loss in the amount of blue light and red light, resulting in an overall loss in light amount. Here, the amount of red light can be increased by using a mirror box 11 that has the spectral reflection characteristics shown in FIG. The amount is small, and only a small amount of light loss is required.

As mentioned above, the adjustment of the light control filter is necessary when you change the production batch or type of color paper used, when you change the developing conditions, when you change the type of film to be printed, or when you change the tungsten light bulb of the light source. This is done when changing the mirror box, etc., but the loss of light amount is reduced by selecting the one that minimizes the amount of dimmer filter inserted into the optical path among the three types of mirror boxes.

According to this embodiment, by selecting the mirror box 11 that minimizes the amount of light control filters 18 inserted into the optical path, the loss of the amount of light from the light source is reduced, and the amount of light irradiated onto the color paper is increased compared to the conventional method. As a result, the set exposure time can be shortened, and the entire print exposure work can be performed in a shorter time.

Please note that even if it is not possible to set the standard negative film exposure time shorter than a certain level due to the structure of the printer's hardware,
Since the exposure time for high-density original plates that require a long exposure time can be shortened, the overall printing time can be shortened.

In addition, in the embodiment, a mirror box 11 having three types of reflecting surfaces with different spectral reflection characteristics has been described, but the invention is not limited to the above-mentioned spectral reflection characteristics and types, and two or four or more types of mirrors may be used. A box 11 may also be provided. With recent vacuum evaporation methods, it is possible to easily create reflective surfaces with almost the desired spectral reflection characteristics, so mirror boxes 11 with various spectral reflection characteristics can be created.
It is more effective to prepare a large number of methods in advance and select one from among them. Furthermore, if the required characteristics are known in advance, a mirror box 11 having specific spectral reflection characteristics may be prepared.

Also, instead of replacing the entire mirror box 11,
You can also replace the reflective surface.

In the present invention, mirror boxes having different spectral reflection characteristics are selected for use, but it is also possible to select from tungsten light bulbs with cold mirrors having different spectral reflection characteristics. However, this is not preferable because it is difficult to manufacture and increases cost.

Although the above description has been made regarding a subtractive color printer, it can also be applied to an additive color printer.

Further, the present invention can be applied not only to printers having separate light control filters and cut filters, but also to printers in which a set of three color filters serves as both a light control filter and a cut filter.

According to the above embodiment, a mirror box that reduces the amount of dimmer filter inserted into the optical path is selectively used, so the lighting voltage of the tungsten bulb can be lowered to stabilize it for a long period of time, and the tungsten bulb consumes less power and generates less heat. The effect is that it can also be used.

〔Effect of the invention〕

The present invention reduces the amount of light control filter inserted into the optical path and selectively uses a mirror box, which reduces light loss in the light source device, shortens print exposure time, and improves efficiency. This effect can be obtained.

[Brief explanation of drawings]

Fig. 1 is a spectral reflection characteristic curve of the reflective surface inside a mirror box according to an embodiment of the present invention, Fig. 2 is a schematic cross-sectional view of the light source section, Fig. 3 is a specific energy curve of a tungsten light bulb, and Fig. 4 is The spectral sensitivity characteristic curve of color paper, FIG. 5 shows the spectral reflection characteristic curve of the cold mirror's spectral response and its repetition, and FIG. 7 shows the spectral transmission and reflection characteristic curve of the Guicreitta filter. 11...Mirror box, 12...Diffusion plate, 14...Cold mirror, 16...Tungsten light bulb, 18...Dimmer filter 20...Cut filter diagram attached table 1n m+ Diagram J & Gloss m) Fig. Fig. Fig. Arm length (nm + Fig. A)

Claims (1)

[Claims] (1) A light source that generates white light, a cylindrical mirror box with a reflective surface formed on its inner surface, and a cylindrical mirror box that is arranged between the light source and the mirror box to balance the color of the light that enters the mirror box. A light source device for a photographic printer, which is equipped with a light control filter to be adjusted, is characterized in that a plurality of mirror boxes each having different spectral reflection characteristics are prepared, and a specific mirror box is selected from the plurality of mirror boxes for use. Light source device for photo printing equipment.