JPS60233634A - Exposing device for copying machine - Google Patents

Abstract

PURPOSE:To form an optimum image on a photosensitive surface by providing light distributing members to flash light sources and irradiating light more from both side edges thereby irradiating more light to the circumferential edge part of a platen than to the central part. CONSTITUTION:Platen glass 2 is provided in the upper part of a housing 1 and a pair of the flash light sources 6a, 6b are provided on the inside wall surface facing each other. Reflectors 7a, 7b are provided to the flash light sources 6a, 6b and the distributing members 20 are provided to the apertures of the reflectors 7a, 7b and are so opened that the more light is emitted from both side edge parts 23 than from the central part 21. The illuminance at the circumferential edge of the platen 2 increases when the light is irradiated from the light sources 6a, 6b to the platen 2. The light passes through an imaging lens 4 and is projected to the photosensitive surface 5. The image projected on the surface 5 is more uniform as the illuminance at the circumferential edge of the platen 2 is higher than the central part. The irradiation is made more from both side edges of the light sources than from the central part and therefore the optimum irradiating distribution is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exposure device for a copying machine, and particularly relates to an improvement in an exposure device of a type that illuminates a platen mainly from two directions and employs a so-called full exposure method. .

[Prior art]

In a copying machine, a conventional exposure device that employs a full-surface exposure method has a housing (1) with a closed cross-section structure that blocks external light, as shown in FIGS. 1 and 2, for example. A rectangular opening is provided at the top (la) of the housing (1), and a platen (3) made of glass or the like on which an object (2) such as a manuscript is placed is inserted into the opening. A lens mounting hole is provided in the bottom (1b) of 1), and the imaging lens (4) is inserted into the lens mounting hole, while a flash illumination means (S) is installed inside the housing (IJ). This exposure device simultaneously illuminates the entire surface of the platen (3) with a flash illumination means (S) during exposure, and illuminates the object (2) on the illuminated platen (3). ) is projected onto a predetermined photosensitive surface (5) via the imaging lens (4).

In such a conventional exposure device, if the illuminance distribution of the projected image on the photosensitive surface (5) is uneven, unevenness or bright lines may occur in the copied image, which may impair the quality of the copied image. It is necessary to keep the illuminance distribution of the projected image on the photosensitive surface (5) uniform. In this case, the imaging lens (4) has a cosine-fourth power side characteristic, that is, the amount of light of the projected image passing through the imaging lens (4) decreases by cos'θ depending on the incident angle (θ). Because of this characteristic, even if the illuminance distribution on the platen (3) surface is simply kept uniform, the illuminance distribution of the projected image on the photosensitive surface (5) cannot be kept uniform. For this reason, conventional exposure apparatuses usually use a flash illumination means (81) that takes into consideration the characteristics of the imaging lens (4) to give the illuminance distribution on the platen (3) surface a state of excessive periphery. This corrects the characteristics of the imaging lens (4) to maintain a uniform illuminance distribution of the projected image on the photosensitive surface (5).

Conventionally, among this type of flash lighting means, the platen (
An example of a method for illuminating 3) primarily from two directions is disclosed in Japanese Patent Laid-Open No. 58-517F31. As shown in FIGS. 1 and 2, this flash illumination means (S) is located on the side circumference (1c) of the housing (1).
A pair of flash light sources (6a
) (6b) and this flash light source (6a) (6b)
Each flash light source (6a) (
main reflectors (7a) (7b) that guide the light from the housing (1) toward the entire surface of the platen (3);
1, and plate-shaped auxiliary reflectors ('8a) and (8b) installed at the inner wall surface of the platen (3) along the other opposite side edges of the platen (3). There is.

According to such a flash illumination means, when the flash light sources (6a) (6b) emit light during exposure, most of the light from the flash light sources (6a) (6b) is transmitted directly or directly to the main reflector (7a). ) (7b) and then reaches the platen (3) surface, and part of the light from the flash light sources (6a) (6b) is reflected by the auxiliary reflectors (8a) and (8b) and then reaches the platen (3).
reach the surface.

In this case, from the flash light sources (6a) (6b),
Direct light and reflected light from the main reflectors (7a) (7b) are mainly caused by flash light sources (6a) (
A portion of the light reflected from the auxiliary reflectors (8a, 8b) that brightly illuminates both side edges of the platen (3) along the axial direction of the platen (6b, ) is mainly reflected from the platen (6b, ) due to the optical path length.
Since the other side edges of the platen (3) are brightly illuminated,
) The illuminance distribution on the surface is given in a state of excessive periphery.

However, in such a conventional exposure apparatus, the flash light sources (6a) and (6b) are usually designed to emit a uniform amount of light along the axial direction, so the auxiliary reflector (8a) ) (8b), it is not possible to ensure a wide illuminance difference on the platen (3) surface in the direction along the axial direction of the flash light sources (6a) (6b). Therefore, among the peripheral parts of the platen (3) surface, especially the part farthest from the flash light sources (6a) (6b), that is, the part of the platen (3) perpendicular to the axial direction of the flash light sources (6a) (6b). Not only does the illuminance at the center of both edges tend to be insufficient compared to the reference illuminance at the center of the platen (3), but the angle of incidence (θ) of the projected image on the imaging lens (4) ) is maximum, in other words, this is the area that requires the greatest illuminance to correct the characteristics of the imaging lens (4), so the illuminance at the corner is also the same as the reference illuminance at the center of the platen (3). However, it tends to be insufficient. As a result, the characteristics of the imaging lens (4) cannot be reliably corrected, and the illuminance distribution of the projected image on the photosensitive surface (5) tends to become uneven, which may impair the quality of the copied image. .

As a means to solve this situation, it is conceivable to give desired light distribution characteristics to the flash light sources (6a) and (6b) themselves by arranging a plurality of filaments at desired positions, for example, but in this case, Since the structure of the flash light sources (6a) (6b) themselves becomes complicated, the cost of the flash light sources (6a) (6b) themselves increases, and the exposure apparatus itself also becomes expensive accordingly. .

[Purpose of the invention]

This invention was made based on the above points,
The purpose of this is based on a type that illuminates the platen surface mainly from two directions, and it is possible to reliably correct the characteristics of the imaging lens without unnecessarily increasing the cost of the device itself, and thereby An object of the present invention is to provide an exposure device for a copying machine that can always maintain a uniform illuminance distribution of a projected image.

[Structure of the invention]

The basic configuration of the present invention is that flash light sources are respectively installed on the inner wall surface of the side circumferential portion of the housing along opposite opposite side edges of the platen, and that light from each flash light source is directed toward the entire surface of the platen. In the flash illumination means, the light from the flash light source is distributed between the flash light source and the platen toward both side edges of the platen perpendicular to the axial direction of the flash light source. A light distribution member is provided.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

In the embodiment shown in FIGS. 8 and 4, the exposure device is
As in the past, the top of the housing (1) with a closed cross-section structure (
1a) is provided with a platen (3), an imaging lens (4) is provided on the bottom (1b) of the housing (1), and a flash illumination means (S) is provided inside the housing (1).
It is made by arranging.

In this embodiment, as in the conventional case, the flash illumination means (S) are provided at portions of the inner wall surface of the side circumferential portion (lc) of the housing (1) along opposite opposite side edges of the platen (3). A pair of flash light sources (6a) (6b) installed and emitting a uniform amount of light along the axial direction; and a pair of flash light sources (6a) (6b) installed along the axial direction of the flash light sources (6a) (6b). substantially semi-cylindrical main reflectors (7a) (7b) that guide the light from the platen (3) toward the entire surface of the platen (3); It is equipped with flat plate-shaped auxiliary reflectors (8a) (8b) respectively installed along the opposite opposite side edges of the flash light source (6a) (6b) and the platen (8a) (8b). 3), a light distribution member (2) is provided between each of them. This light distribution member ■ is the main reflector (7aχ7b
) has a rectangular base plate Qη that covers the opening facing the platen (3) of the main reflector (7).
a) It is attached by fastening to the upper edge of (7b). The base play Hη is provided with a light transmission port (A), and the light transmission port (2) is symmetrical along the axial direction of the flash light source (6aχ6b) with the center of the base play H1) as the border. It is formed in a shape that widens at the end.

Note that if the reflected light from the platen (3) surface directly enters the imaging lens (4), the illuminance distribution of the projected image on the photosensitive surface (5) will become uneven. 6a) and (6b), the reflected light is directly transmitted to the imaging lens (4).
) are placed in positions that do not fit.

Therefore, according to the exposure apparatus according to the embodiment (g), when the flash light sources (6a) (6b) emit light during exposure,
The direct light from the flash light source (61L) (6b) and the reflected light from the main reflectors (7a) (7b) are transmitted through the light distribution member (
The light is irradiated into the housing (1) through the light transmission opening (a) of (b). At this time, the light intensity distribution along the axial direction of the flash light sources (6a) (6b) immediately after passing through the light distribution member (vertical axis C: light intensity, horizontal axis 2: axial position of the flash light source) is As shown in FIG. 5, the opening area of the light transmitting aperture increases gradually from the center to the periphery. Therefore, most of the light that has passed through the light distribution member (A) directly reaches the entire surface of the platen (3) with the above-mentioned light intensity distribution characteristics, and the light distribution member (A)
A part of the light passing through the auxiliary reflectors (8a) (8b)
After being reflected, it reaches the platen (3) surface. in this case,
Both side edges of the platen (3) along the axial direction of the flash light sources (6a) (6b) are connected to the flash light sources (6a) (6b).
b,), the amount of light irradiated to both side edges is more than the amount of light irradiated to the center of the platen +31, while the direction perpendicular to the axial direction of the flash light sources (6a) (6b) Depending on the light distribution characteristics of the light distribution member (20), the platen (3) is attached to both side edges of the platen (3).
A larger amount of irradiation light will be distributed to the center. Therefore, the illuminance distribution on the platen (3) surface is as shown in Figure 6 Fa.
) is given in a state of peripheral overload.

In the illuminance distribution on the platen (3) surface, due to the light distribution characteristics of the light distribution member (company), the illuminance distribution on the platen (3) surface in the direction along the axial direction of the flash light sources (6a) (6b) is different from that in the past. The difference in illuminance is maintained to a certain extent. Therefore, among the peripheral parts of the platen (3) surface, especially the part farthest from the flash light sources (6a) (6b), that is, the part of the platen (3) perpendicular to the axial direction of the flash light sources (6a) (6b). As shown in FIG. 6(b), the illuminance L1 at the center of both side edges is equal to the reference illuminance at the center of the platen (3). FIG. 6 (al As shown in and tel, the illuminance L2 at the corner is equal to the reference illuminance at the center of the platen (3).

This means that there is a sufficient illuminance difference ΔL2. Therefore, a situation in which the peripheral illuminance of the platen (3) is insufficient with respect to the reference illuminance at the center of the platen (3) can be effectively avoided.

In this way, since the desired illuminance distribution is obtained on the surface of the platen (3), the original image of the object (2) to be copied on the platen (3) illuminated with the illuminance distribution illuminates the imaging lens (4). Even if it is projected onto the photosensitive surface (5) through
The characteristics of the imaging lens (4) are effectively corrected, and the illuminance distribution of the projected image on the photosensitive surface (5) is always kept uniform.

Note that the light distribution members (20) are not necessarily limited to those shown in the above embodiments; for example, as shown in FIG. shaped light transmission openings (28a) (23a
), or if it is desired to further reduce the light directed toward the center of the platen (3), the
As shown in (b), a light shielding plate (c) that blocks light directed toward the center of the platen (3) may be added to the light distribution member @) shown in the embodiment, which may impair the light distribution characteristics. You may change the design as appropriate to the extent that there is no problem. Furthermore, in the above embodiment, the flash light sources (6a) (6b) are of a type that emits a uniform amount of light along the axial direction, but filament type flash light sources (6a) (6b) may also be used. . In this case, the amount of light irradiated in the axial direction of the flash light sources (6a) (6b) will change, so it is necessary to take this into account and set the light distribution member (4) to a desired value.

Further, in the above embodiment, the flash light sources (6a) (6b) along the negative side edge of the platen (3) are composed of one, but this is not limited to this, and as shown in FIG. There is no problem even if it consists of multiple copies of each. Furthermore, in the above embodiment, the light distribution member @) is the main frame (7a) (7b
), but it is not necessarily limited to this, and the light distribution member (Inc.) may be attached to the housing (1). Further, in the above embodiment, the main reflector (7a) (7
The specific shapes of b) and the auxiliary reflectors (8a) and (8b) may be modified as appropriate, and the auxiliary reflectors (8a) and (8b) are not necessarily necessary in this invention. Also, regarding other parts of the exposure device,
It goes without saying that the design is not limited to that shown in the above embodiments, and the design can be changed as appropriate.

〔Effect of the invention〕

As described above, according to the exposure device for a copying machine according to the present invention, by setting the light distribution characteristics of the light distribution member to a desired value, the light distribution to the platen surface can be freely adjusted. It is now possible to optimize the illuminance distribution on the platen surface, and along with this, the characteristics of the imaging lens can be reliably corrected, and the illuminance distribution of the projected image on the photosensitive surface can be kept uniform at all times. . Further, according to the present invention, since it is sufficient to attach a light distribution member with a simple structure to the existing flash illumination means, there is no need to complicate the structure of the flash light source itself, and the cost of the exposure apparatus itself becomes unnecessary. There is no concern that it will bulk up.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a conventional exposure device for a copying machine, FIG. 2 is a sectional view taken along line H-H in FIG. 1, and FIG. 3 is an embodiment of the exposure device for a copying machine according to the present invention. FIG. 4 is an exploded perspective view of the main parts, FIG. 5 is an explanatory diagram showing the light distribution characteristics of the light distribution member, and FIG. 6(a) is the illuminance on the platen surface. Explanatory diagram showing the distribution, Figure 6(b) and t
el is an explanatory diagram showing the distribution of illuminance along the X-X line and the x'-x' line in Figure 6 fal, Figure 7, and Figure 8 (a
l is a perspective view showing a modified example of the light distribution member, FIG. 8(b)
8A is a cross-sectional explanatory view of FIG. 8(a), and FIG. 9 is a perspective view showing a modification of the arrangement of the flash light source. Code explanation

Claims (1)

[Claims] - A housing with a closed cross-section structure, a platen that is attached to a rectangular opening provided at the top of the housing and forms a surface for placing a copying object and is made of a transparent material, and a platen that is disposed inside the housing. The apparatus comprises a flash illumination means for instantaneously illuminating the entire surface of the platen, and an imaging lens attached to a hole formed in the bottom center of the housing, and an object to be copied on the platen illuminated by the flash illumination means. In the exposure device for a copying machine, the original image of the image is projected onto a predetermined photosensitive surface through the imaging lens, and the flash illumination means is arranged on both opposite sides of the platen on the inner wall surface of the side circumference of the housing. flash light sources installed at respective locations along the edge; a reflector member that guides light from each flash light source toward the entire surface of the platen;
and a light distribution member disposed between the flash light source and the platen and distributing more light from the flash light source toward both side edges of the platen perpendicular to the axial direction of the flash light source. Features: Copying machine exposure device.