JPH01193835A - Photograph printing device - Google Patents

Abstract

PURPOSE:To remove the unevenness of exposure caused by incomplete diffusion by bending an outgoing side diffusion plate so that the side facing a printing lens becomes concave. CONSTITUTION:The diffusion box 12 is arranged between a negative film 10 and a light source 11 and printing light is fully diffused in the diffusion box 12 so as to light the negative film 10, then a negative image is printed on photographic paper 14 by the printing lens 13. The diffusion box 12 is constituted of a square pillar 20 whose inner surfaces are reflecting surfaces, an incidence side diffusion plate 21 attached to the lower end of said pillar 20 and the outgoing side diffusion plate 25 attached to the upper part thereof and the side, facing to the printing lens 13, of the outgoing side diffusion plate 25 is made concave. As a result, the ellipse of the luminance distribution inclines toward the optical axis 18 of the printing lens 13 and the luminous flux whose intensity is intense is made incident on the printing lens 13 even in the peripheral part of the outgoing side diffusion plate 25 to contribute the exposure of the photographic paper 14. Thus, the unevenness of exposure caused by the incomplete diffusion can be prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photographic printing apparatus, and more particularly to a photographic printing apparatus having an improved illumination system for negative film.

[Conventional technology]

As shown in FIG. 2, in a conventional photographic printing apparatus, a diffusion box 12 is disposed between a negative film 10 and a light source 11 in order to prevent uneven exposure (light source unevenness).

The printing light illuminates the negative film 10 after being sufficiently diffused within the diffusion box 12. This negative film 1
The negative image recorded at 0 is printed onto photographic paper 14 by a printing lens 13. Further, in order to effectively utilize the light emitted from the light source 11, a reflector 15 is arranged behind the light source 11. In addition, code 16.1
7 is a mask, and a shutter is arranged between the printing lens 13 and the photographic paper 14.

The diffusion box 12 is a device consisting of a rectangular tube 20 whose inner surface is a reflective surface, such as a mirror surface or a diffused reflection surface, an incident side diffuser Fi 21 attached to the lower end of the rectangular tube 20, and an exit side diffuser plate 22 attached to the upper tj. This incident side diffuser plate 21 is
Satin glass is used, and the exit side diffuser plate 22 is made of a milky white plastic plate. The light from the light source 11 is scattered and transmitted by the incident-side diffuser plate 21, and is repeatedly reflected within the rectangular tube 20 until it reaches the exit-side diffuser plate 22, where it is scattered and transmitted again.

[Problem to be solved by the invention]

In ideal diffusion, the intensity distribution (light distribution characteristics) for a unit minute area on the exit side diffuser plate 22 is circular, but in reality, the diffusion is incomplete, as shown in Figure 2. The intensity distribution becomes an ellipse 23. With this incomplete diffusion, the brightness on the diffusing surface becomes uniform regardless of its position, but when the diffused light is made to enter the printing lens 13, the brightness increases as the distance from the optical axis 18 of the printing lens 13 increases. Only weak light enters the burning lens 13.

Therefore, a decrease in the amount of light occurs at the peripheral portion of the diffusion surface, which causes exposure unevenness.

Note that it is possible to increase the thickness of the exit-side diffuser plate 22 to bring it closer to complete diffusion, but this will cause a vicious cycle in which the amount of transmitted light will decrease and the efficiency will drop significantly.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a photographic printing apparatus that eliminates exposure unevenness caused by incomplete diffusion.

[Means for Solving the Problems] In order to achieve the above object, the present invention is such that the exit side diffuser plate is curved so that the printed lens side has a concave surface.

In order to efficiently condense light using the exit side diffuser plate, it is preferable that the center of its curvature be the principal point of the printing lens.

[Function] Since the exit-side diffuser plate is concavely curved, the elliptical shape of the brightness distribution is inclined toward the optical axis of the printed lens.

Therefore, even in the periphery of the exit-side diffuser plate, a high-intensity light beam enters the printing lens and contributes to the exposure of the photographic paper, making it possible to eliminate exposure unevenness due to incomplete diffusion.

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment) FIG. 1 shows a photoprinting apparatus of the present invention, and FIG.
Components that are the same as those shown in the figures are given the same reference numerals and their explanations will be omitted. The exit side diffuser plate 25 of the present invention has a curved surface concave toward the printing lens side, and focuses the light emitted from it on the printing lens 13. In order to efficiently condense the light, the center of curvature of the curved surface is made to coincide with the principal point of the printing lens 13.

As described above, in the present invention, the exit-side diffuser plate 25 has a concave shape, but the luminance distribution in a small area taken on the outer surface becomes an elliptical shape 26, and incomplete diffusion still occurs. However, since the condensing effect of the concave surface of the exit-side diffuser plate 25 bends the optical path, the luminance distribution around it bends into an elliptical shape 2.
6 is in a state of being tilted toward the principal point of the baked lens 13. Therefore, among the light beams emitted in various directions from the exit-side diffuser plate 25, the light beam with the strongest intensity, which corresponds to the long sleeve of the ellipse 26, enters the negative film IO, and the light that passes through it is transmitted to the printing lens 13. The light enters the photographic paper 14 through the. As a result, the intensity of the point Q on the optical axis 18 and the point P on the periphery of the negative film 10 becomes almost the same, so that exposure unevenness can be eliminated.

[Effects of the Invention] As explained in detail above, in the present invention, the diffusion plate disposed on the exit side of the diffusion box has a concave shape, so that after incompletely diffused light, a strong light beam passes through the negative film. , exposure unevenness caused by incomplete diffusion can be eliminated. Furthermore, since the thickness of the diffuser plate may be increased, the amount of light from the light source can be used effectively.

Furthermore, since the center of curvature of the exit-side diffuser plate coincides with the principal point of the baked lens, it is possible to utilize the light flux with the highest intensity among the incompletely diffused light.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the photographic printing apparatus of the present invention. FIG. 2 is a schematic diagram of a conventional photographic printing apparatus. 10...Negative film 11...Light source 12...Diffusion box 13...Printing lens 14...Photographic paper 21...Incidence side diffusion plate 22...Emission side diffusion plate 25...Emission Side diffuser. Figure 1

Claims (2)

[Claims] (1) A photographic printing apparatus in which printing light emitted from a light source is diffused by a diffusing means and then illuminated on a negative film, and a negative image recorded on the negative film is printed onto photographic paper via a printing lens, The means consists of a rectangular tube whose inner surface is a reflective surface, an entrance side diffuser plate placed at the end of the rectangular tube on the light source side, and an exit side diffuser plate placed at the end of the printed lens side. A photographic printing device characterized in that the diffusion plate is curved so that the printing lens side has a concave surface. (2) The photographic printing apparatus according to claim 1, wherein the exit side diffuser plate is curved so that its center of curvature coincides with the principal point of the printing lens.