JP2512070Y2 - Flash exposure device for plate making camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> This invention relates to a flash exposure apparatus for a plate making camera.

<< Prior Art >> An auxiliary exposure method is one of the methods for controlling the contrast of a halftone negative image in response to various originals when halftone imaging is performed by a plate making camera.

This method is generally used for halftone shooting using a negative contact screen, a main exposure, a highlight exposure without a screen that increases the contrast from the light part to the middle part of the document, and a dark part to the middle part of the document. In order to soften the contrast over time, the screen consists of flash exposure that provides uniform exposure over the entire film, and the main exposure and highlight exposure or flash exposure are appropriately combined to correspond to the contrast of the original. This is a method of obtaining a halftone negative image.

As a flash exposure apparatus for giving the above flash exposure, a flash exposure apparatus shown in FIG.
7), or the one indicated by reference numeral 51 in FIG. 7 (hereinafter referred to as Conventional Example 2) is known.

The first conventional example is a light source lamp 42 that is dimmed through an automatic light control device (not shown), a lamp case 43 that covers the light source lamp 42, and a light shield plate that is mounted in an opening in the front of the lamp case 43. 44, a diffuser plate 45 and a monochromatic filter 46,
It is arranged adjacent to the imaging lens in the lens rack of the plate-making camera, and is configured so that the light amount can be controlled according to the photographing magnification.

As shown in FIG. 6, the light shielding plate 44 is formed by arranging a large number of light transmitting holes 44a through which light from the light source lamp 42 passes in a circular shape with a predetermined radius. The light transmitting plate 45 passes through the light transmitting holes 44a. It gives directivity to the light diffused by. That is, the illuminance distribution on the irradiated surface is configured to be substantially uniform over the entire surface by suppressing the increase in the central portion.

Further, the monochromatic filter 46 is, for example, a green filter, and since the color temperature of the light source lamp 42 changes in accordance with the dimming, the monochromatic color of the flash exposure is obtained by interposing the monochromatic filter 46. This is to eliminate the adverse effects associated with dimming in consideration of the case where an off-soiling film or a panchromatic film having different sensitivities depending on the photosensitive wavelength range is used together.

The conventional example 2 is arranged in the lens frame 9 of the plate-making camera,
It is provided with four light source lamps 52 that are dimmed through an automatic light control device (not shown), and a transmission type diffuser umbrella 53 that covers the light source lamps 52 as a set of two, and the conventional example 1 Similarly, the light amount can be controlled so that the illuminance is constant on the image projection surface even if the photographing magnification changes.

The transmission type diffuser umbrella 53 is integrally injection-molded as shown in FIG. 8, and the light of each light source lamp 52 is diffused almost uniformly in all directions by a hemispherical light diffusing portion 53a. Since it is not possible to make the illuminance distribution on the illuminated surface uniform with only one lamp, the four light source lamps 52 are arranged symmetrically with respect to the imaging lens 10 with respect to the optical axis, and are arranged apart from each other to obtain a uniform illuminance distribution. Is done. The reference numerals in FIG. 7
Reference numeral 15 is a filter turret provided with color separation filters 16.

<< Problems to be Solved by the Invention >> Although the above-mentioned conventional example 1 is excellent in that a uniform illuminance distribution can be obtained, since less than 10% of the light emitted from the light source lamp can be used, Long exposure time,
Moreover, since the lamp case 43 and the light shielding plate 44 are separately processed and assembled, the cost is high.

On the other hand, in the conventional example 2, since the transmission type diffuser umbrella 53 is used in place of the lamp case 43, the four light source lamps 52 ...
A uniform illuminance distribution cannot be obtained unless they are spaced apart. Therefore, the cost is high as a whole.

The present invention was made in consideration of such circumstances,
It is a technical object to provide a flash exposure apparatus which can obtain a uniform illuminance distribution as a single unit of the flash exposure apparatus and can be implemented at low cost.

<< Means for Solving the Problems >> The present invention is configured as follows to solve the above problems.

That is, a flash exposure apparatus for a plate making camera, comprising a light source lamp arranged in a lens frame of the plate making camera and a transmissive diffuser umbrella covering the light source lamp, wherein the transmissive diffuser umbrella is formed in a truncated cone shape. It is characterized in that the entire top surface of the truncated cone of the diffusing umbrella is shielded from light and that the peripheral side surface is capable of diffusing light.

It should be noted that the term “shading” as used herein includes not only complete shading but also dimming.

<Operation> In the present invention, the transmissive diffuser is formed in a truncated cone shape, and the light emitted from the light source lamp is shielded by the top surface of the truncated cone of the diffuser and scattered by the peripheral side surface. That is, since the light scattered on the peripheral side surface has a small component toward the central portion of the irradiated surface and a large component toward the peripheral portion, the illuminance distribution over the entire effective size of the irradiated surface becomes substantially uniform. The transmissive diffuser has a simple shape and is easy to manufacture.

<< Embodiment >> FIG. 1 is a perspective view of a flash exposure apparatus according to the present invention.
FIG. 2 is a plan view of the inside of the lens rack, and FIG. 3 is a perspective view of a vertical plate-making camera equipped with the flash exposure apparatus according to the present invention.

 First, the vertical plate-making camera will be briefly described.

As shown in FIG. 3, this vertical plate-making camera has a photographing frame 3 provided on an upper opening frame 2 of a substantially U-shaped base frame 1, and a lens frame 9 and a document frame 20 which are vertically movable. It is configured.

The photographing rack 3 hinges a focus glass 4 to the right side of the upper opening frame 2 and a film suction plate 5 to the left side of the upper opening frame 2 in a rotatable manner, and selectively rotates the focus glass 4 and the film suction plate 5. And is positioned on the image plane. In FIG. 2, reference numeral 6 is an operation panel, and 7a and 7b are densitometers 7.
Is a light-emitting window and a photometric probe.

The lens frame 9 is connected to the photographing frame 3 via the bellows 8. Further, a plurality of imaging lenses 10 are mounted on the central portion of the lower surface of the lens frame 9 so that the lenses can be exchanged to cover a required photographing magnification range. I'm supposed to get it. A pair of left and right flash exposure devices 11, 11 and a filter turret 15 having a color separation filter are additionally provided inside the lens frame 9.

The document rack 20 is provided with a document table 21 that can be moved up and down, a document pressure bonding glass plate 22, a pair of reflected illumination light sources 24 and 24 supported by the document table 21 via a light source arm 23, and the lower surface of the document table 21. And a transillumination light source (not shown) attached to
The document table 11 is positioned together with the lens rack 9 via an automatic focusing mechanism (not shown) so that the document on the document table 21 can be photographed at a desired magnification.

The flash exposure apparatus according to the present invention will be described below.

The flash exposure apparatus 11 includes a pair of left and right imaging lenses 10 in the lens frame 9 of the plate making camera as described above.
Are located close to each flash exposure device 11
Is a light source lamp 12 and a transmissive diffuser umbrella that covers the light source lamp 12.
13 is provided, and the illuminance of the light source lamp 12 itself is constant,
The exposure time can be adjusted according to the photographing magnification, the sensitive material used, and the like.

Green paint is applied to the surface of the light source lamp 12,
It is configured to prevent adverse effects due to color temperature changes due to light source deterioration. The green paint functions as a monochromatic filter.

As shown in FIG. 1, the transmission type diffuser umbrella 13 is formed in a truncated cone shape, and the entire surface of the truncated cone top surface 13a is shielded by a light shielding seal 14, and the light emitted from the light source lamp 13 at the peripheral side surface 13b. Is configured to scatter light.

Reference numeral 13c in FIG. 1 is a fixing collar portion of the diffuser.

According to this transmissive diffuser, the component of the light scattered on the peripheral side surface 13b toward the irradiated surface (sensitive material holding surface) of the imaging rack 3 is small and the component toward the peripheral portion is large, so that The illuminance distribution over the entire effective size of the irradiation surface becomes almost uniform.
In this embodiment, two flash exposure devices are arranged in a pair on the left and right in order to shorten the flash exposure time. However, in order to obtain a uniform illuminance distribution with a single flash exposure device, a transmission type diffuser umbrella is used. Since the shape is set,
The number can be increased or decreased as appropriate.

By the way, the transmission type diffuser umbrella 13 has a truncated cone whose height is H.
= 5 cm, top diameter D ₁ = 3 cm, bottom diameter D ₂ = 4 cm,
The wall thickness of the peripheral diffuser is set to 1.5 mm, and it is injection molded from a milky white synthetic resin material. Note that FIG. 4 is a graph illustrating the illuminance distribution on the illuminated surface of the vertical plate-making camera shown in FIG. In this figure, the solid line shows the illuminance distribution according to the present embodiment, and the broken line shows the illuminance distribution according to the conventional example of FIG. 7, showing that the illuminance distribution over the entire illuminated surface is improved well.

In the above embodiment, the case where the size and shape of the truncated cone is specified has been illustrated on the assumption that it is applied to the vertical plate-making camera of FIG. 3, but the present invention is not limited to this, and the model of the plate-making camera or The shape of the truncated cone can be changed as appropriate according to the size of the surface to be irradiated.

Further, in the above-mentioned embodiment, the case where the green paint is applied to the surface of the light source lamp is illustrated, but the green paint may be applied to the peripheral side surface of the transmissive diffuser.

<Effects of the Invention> As is clear from the above description, in the present invention, the transmissive diffuser umbrella is formed in a truncated cone shape, and the irradiation surface is illuminated by the light scattered on the peripheral side surface. Has a great effect.

I. Since most of the light emitted from the light source lamp toward the peripheral side surface of the diffuser can be used, the light is brighter and the exposure time can be shortened as compared with Conventional Example 1.

B. Since a uniform illuminance distribution can be obtained even with the flash exposure apparatus alone, it is not necessary to dispose four pieces apart as in the conventional example 2.

C. Moreover, since the transmissive diffuser has a simple shape, it can be implemented at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view of a flash exposure apparatus according to the present invention, FIG. 2 is a plan view of the inside of a lens rack, FIG. 3 is a perspective view of a vertical plate-making camera equipped with the flash exposure apparatus according to the present invention, and FIG. Is an illuminance distribution diagram on the illuminated surface, FIG. 5 is a vertical cross-sectional view of Conventional Example 1, FIG. 6 is a plan view of the light shielding plate in FIG. 5, and FIG. 7 is equivalent to FIG. 2 of Conventional Example 2. 8 and 9 are perspective views of the transmissive diffuser in FIG. 9 ... Lens rack, 11 ... Flash exposure device, 12 ... Light source lamp, 13 ... Transmission type diffuser umbrella, 13a ... Cone top surface, 1
3b …… The peripheral side of the truncated cone.

Claims (1)

(57) [Scope of utility model registration request] 1. A flash exposure apparatus for a plate making camera comprising a light source lamp arranged in a lens frame of the plate making camera and a transmissive diffuser umbrella covering the light source lamp, wherein the transmissive diffuser umbrella has a truncated cone shape. The light exposure device for a plate making camera is characterized in that it is configured to block the entire top surface of the truncated cone of the diffusing umbrella and to diffuse light on the peripheral side surface.