JPH0348491B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flash exposure apparatus having a uniform illuminance distribution.

Continuously lit light sources such as tungsten lamps, metal halide lamps, and xenon arc lamps have been widely used in full-surface exposure for recording using photosensitive or heat-sensitive recording materials. On the other hand,
A light source using a flash discharge tube that can emit high-energy light in a short period of time has also been proposed.

The entire surface exposure apparatus used for recording on the various recording materials described above is required to have a uniform illuminance distribution over the area required for exposure. Incidentally, a flash discharge tube is a linear light source having a concentric illuminance distribution around the tube, and the longer the arc length, the more pronounced the cylindrical illuminance distribution becomes.

As a method for making the illuminance distribution uniform in an exposure apparatus using a discharge tube with a relatively long arc length, various methods have been proposed in which the shape of the reflector plate is devised. According to Japanese Patent Application Laid-Open No. 48-97548, a flash discharge tube with a diameter D is installed at a position offset from the focal point of a reflector whose cross-sectional area outline is a parabola by about 1/2 D toward the bottom of the reflector, and A flash-type light source device has been proposed in which the side surface in contact with the discharge tube at right angles is a flat surface and specularly reflects, and the portion parallel to the discharge tube is at least diffusely reflected at the bottom. When irradiating at the same time, the discharge tube distance should be set to 8
It is said that uniform irradiation can be obtained when the radiation is set between D and 10D. On the other hand, since a uniform irradiation surface could not be obtained even by using a reflector with a parabolic cross-sectional shape, a device consisting of a reflector with a cross-sectional shape of a curve determined by a special drawing method was developed in JP-A-51-
Proposed in No. 126156. It is stated that a wide irradiation surface can be obtained by combining a plurality of reflecting mirrors according to this proposal and using a large number of discharge tubes.
However, although the proposal in JP-A No. 51-126156 focused only on the specular reflection of the reflecting mirror and processed it, in reality, the disturbance of the specularly reflected light flux by the discharge tube itself cannot be ignored. . Furthermore, it is not only complicated to obtain the cross-sectional curve of the reflecting mirror in this proposal, but also extremely high processing accuracy is required in actual manufacturing of the reflecting mirror.

Furthermore, JP-A-48-97548 and JP-A-51-126156
In any of the proposals, when using multiple discharge tubes to obtain a wide irradiation area, it is recommended to use a reflector for each discharge tube, which is made by connecting one independent reflector to the number of discharge tubes. However, it was impossible to obtain a uniform illuminance distribution because the illuminance decreased on the boundary line between adjacent curved lines that formed the joints of the reflecting mirrors.

The object of the invention is to eliminate the above-mentioned drawbacks and
An object of the present invention is to provide a flash exposure device having a uniform illuminance distribution.

Note that the light diffusion coefficient α used in the description of the present invention is a coefficient expressed by the following formula.

_Y =(1-sinX)〓 Y: Specific _luminous intensity 90° + θ)) However, X ₁ and X ₂ are angles from the direction of specular reflection θ: angle of incidence According to the present invention, as shown in FIG. In a light source device composed of a reflection plate 3 and a flat opening 4,
Light diffusion coefficient α and light reflectance β of the bottom reflector 2
, the distance R between the flat opening glass plate 4 and the center of the discharge tube 1, and the distance P between the discharge tube 1 and the adjacent discharge tube 1, α≦1.0β≧0.7≧0.6P, respectively.
A flash exposure apparatus is provided that can obtain a uniform illuminance distribution on the planar aperture 4 when the following conditions are satisfied.

On the other hand, if a reflector with α>1.0 is used, a uniform illuminance distribution cannot be obtained, and if a reflector with β<0.7 is used, the effective use of the discharge tube's luminous energy will be hindered, and the R If it is <0.6P, the illuminance unevenness on the planar opening 4 due to the cylindrical illuminance distribution of the discharge tube becomes significant, and the object of the present invention cannot be achieved in either case.

Examples of the bottom reflector that satisfies the above-mentioned conditions regarding the light diffusion coefficient α and the light reflectance β include white papers such as art paper, Kent paper, and synthetic paper, white synthetic resin boards such as white acrylic boards, or Metal plates, synthetic resin plates, and wooden plates painted with white paint are used.

The side reflector 3 used in the present invention has a light diffusion coefficient α
It may be greater than 1.0 and is not particularly limited. Further, it does not have to be positioned perpendicularly to the bottom reflector, and even if it is tilted, the effects of the present invention will not be affected in any way. In practice, P is 2D to 15D with respect to the diameter D of the discharge tube.
is preferable, and 4D to 12D are particularly preferable. The distance between the side reflector and the center of the adjacent discharge tube is preferably 1D to 8D, particularly preferably 2D to 5D, relative to the diameter D of the discharge tube. Furthermore, the distance γ between the bottom reflector and the center of the discharge tube preferably satisfies γ≦2R.

The illuminance distribution was confirmed using the halftone area method and the photo sensor method as appropriate. The halftone dot area method utilizes development in which when a recording material is exposed through halftone dots, the halftone dot area of the recorded image obtained changes depending on the exposure amount. The illuminance distribution is expressed by measuring the halftone dot area. In the photo sensor method, a planar opening is divided into a grid pattern, a sensor is placed on each address, and the received light energy at that position is read.

As one of the embodiments of the present invention, in an exposure apparatus in which straight tubular discharge tubes with an outer diameter of 12 mm are installed in parallel, the interval P between the discharge tubes is 90 mm, and the distance R between the center of the discharge tubes and the transparent glass plate 4 is 70 mm. For the bottom reflector plate 2, commercially available art paper having a light diffusion coefficient α=0.3 to 0.4 and a light reflectance β>0.7 was used. FIG. 2 shows a halftone recorded image obtained by exposing a recording material through a flat-mesh negative original with a line count of 177 lines/inch using the above-mentioned exposure apparatus. X ₂ , X ₃ , and X ₄ described in FIG. 2 indicate positions on the glass plate 4 shown in FIG. 1.

In addition, in the exposure apparatus shown in Fig. 1, X ₁ to X ₄
Figure 3 shows the results of determining the intensity of the irradiated light during this period using the photo sensor method.

As a comparative example, an aluminum plate with a light diffusion coefficient α=2 and a light reflectance β>0.7 was used as the reflector plate 2 in the exposure apparatus shown in FIG. 1, and P and R were the same as those in the example. A halftone recorded image obtained in the same manner is shown in FIG.

Further, FIG. 5 shows a halftone dot recorded image when the same art paper as in the example was used as a reflection plate and R=0.5P.

In addition, the copying device Resour Zenofax FX-150 (manufactured by Riso Kagaku Kogyo Co., Ltd.) is manufactured and sold based on the invention described in JP-A No. 48-97548.
FIG. 6 shows a halftone dot recorded image obtained in the same manner as in the above-mentioned example. A, B, and C in the same figure correspond to A, B, and C in the cross-sectional view of the above-mentioned exposure apparatus shown in FIG.
Corresponds to positions B and C.

The change in dot area of the dot recorded image in a constant area obtained in the comparative example was ±2.5 even in the minimum case.
It was %. On the other hand, the change in halftone dot area obtained in the example was less than ±1% at most.

As described above, the exposure apparatus according to the present invention not only has a uniform illuminance distribution over a wide area, but is also advantageous in designing and manufacturing the shape of the reflector, and furthermore, the dot area change is ±1%. The irradiation area S of the planar opening 4 is within the following formula: S = (1-1/2n)n.l., where the effective luminous length of the discharge tube is lmm, the number of discharge tubes is n, and the discharge tube spacing is Pmm. Since it can be expressed as P, the planar opening can be designed accurately and easily.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the exposure apparatus of the present invention, FIG. 2 is a diagram showing a halftone recorded image obtained by the exposure apparatus of the present invention, and FIG. 3 is a diagram showing the irradiation at the plane opening 4 of FIG. Diagrams showing the measurement results of light intensity, Figures 4 and 5
6 and 6 are diagrams showing a halftone dot recorded image according to a comparative example, and FIG. 7 is a conceptual cross-sectional view of a commercially available light source device for a copying machine having a curved reflector.

Claims (1)

[Scope of Claims] 1. In a light source device composed of two or more straight flash discharge tubes, a reflector, and a planar irradiation opening, the discharge tube interval P, the distance R from the center of the discharge tube to the planar opening , between the discharge tube diameter D and the distance r between the bottom reflector and the center of the discharge tube, R≒0.78P, P/D=4 to 12,
The light diffusion coefficient α and the light reflectance β, which have the relationship r≦2R and are expressed by the following formula, are α=
0.3 to 0.4, β>0.7, and a reflecting plate made of a white material is provided at least on the bottom surface of the flash exposure device. _Y =(1-sinX)〓 Y: Specific _luminous intensity 90° + θ)) However, X ₁ and X ₂ are angles from the specular reflection direction. θ: Incident angle.