JPS6024535A - Illuminating device for slit exposure - Google Patents

Abstract

PURPOSE:To give a high slit surface illuminance and a light distribution characteristic which scarcely has an uneven illuminance by constituting so that bulb surfaces of a side for illuminating a slit by a direct projecting light, and a reflector surface side for illuminating a slit by a reflected light by the first reflector become a frosted surface, respectively, and other bulb surface becomes a clear surface. CONSTITUTION:When a bulb surface of a side which faces a slit P of a hologen electric lamp 1 and a reflecting surface 2a of a reflector 2 is made a frosted surface 8, a slit surface illuminance distribution being approximate to a light distribution characteristic of a frost type halogen electric lamp is obtained by illuminating lights F0, F1, respectively. On the other hand, as for a light F2 reflected twice by a reflecting surface 2b and a reflector 3, since an illuminance distribution on the slit surface is equalized by the light distribution characteristic of the halogen electric lamp 1 itself, an uneven illuminance of the slit surface becomes extremely small even if a bulb surface of a side facing it is made a clear surface 9. Also, in case when a bulb surface of a reflecting surface 2c side is made the clear surface 9, the greater part of a light F3 radiated from a filament 7 is returned to the filament 7 side, brightness of the frosted surface 8 is increased, the frosted surface 8 becomes the secondary light source, and the slit surface illuminance is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an illumination device for slit exposure in copying machines, facsimile machines, etc., which is equipped with a non-volatile light bulb.

Structure of the conventional example and its problems A schematic vertical cross section of a conventional slit exposure illumination device for a copying machine is as shown in FIG.

That is, the light emitted from the non-rogen light bulb 1 is focused by the first reflecting mirror 2 and the second reflecting mirror 3, and illuminates the document 6 placed on the contact glass 4 in the form of a slit. The reflected light from P passes through the lens 6 and hits the photoreceptor (
(not shown).

As shown in FIG. 2(a), a conventional light bulb for copying machines has a structure in which the filament 7 is divided into several parts (segmented structure). Halogen light bulbs are thin linear light sources, making it easy to control light distribution, and by changing the composition ratio of segments, the light distribution characteristics in the tube length direction (longitudinal direction of the slit) can be easily changed. It is often used as an exposure light source for copying machines because the length of the bulb, operating voltage, brightness, and power can be set over a wide range.

The exposure illumination device is required to have high illuminance on the slit surface and little unevenness in illuminance in the longitudinal direction of the slit.

The illuminance distribution (light distribution characteristics) in the tube length direction at a certain distance from the bulb surface of a halogen bulb with a transparent bulb (hereinafter referred to as a clear halogen bulb) shows small unevenness changes as shown in the curve in Figure 2 (b). There are many lights, and the illuminance is highly uneven. When such a halogen bulb is used in a lighting device, the illuminance distribution in the longitudinal direction of the slit (slit surface illuminance distribution) naturally has large illuminance unevenness, which causes a significant deterioration in the developed image quality of copies. As a countermeasure for this, the first
Either give the reflector 2 and the second reflector 3 a little diffusivity, or use a halogen bulb with a frosted surface on the entire bulb surface (
(hereinafter referred to as a cross-shaped halogen bulb).

The light distribution characteristic of the 70-stroke halogen light bulb is extremely flat as shown by curve F in FIG. 2(b), and therefore the unevenness of illuminance on the slit surface is also reduced. In addition, in clear type halogen bulbs, the illuminance distribution on the surface changes greatly due to eccentricity of the filament and misalignment of the halogen bulb's mounting position with respect to the first reflector, whereas in frost type halogen bulbs, these changes occur. It has the advantage of having relatively little impact.

However, the slit surface illuminance is significantly lower by 30 to 60% compared to a clear type halogen bulb, and a halogen bulb with a large wattage must be used to obtain a predetermined slit surface illuminance.

On the other hand, if the mirror's specularity is reduced to make it diffusive, the light condensing ability will be reduced and the efficiency of the illumination device will be reduced, so it is not a good idea to reduce the specularity of the reflecting mirror.

OBJECTS OF THE INVENTION The present invention provides a lighting device for slit exposure that can improve the light distribution characteristics in the longitudinal direction of the slit without reducing the slit surface illuminance.

Structure of the Invention The present invention provides a first reflecting mirror having a shape that partially surrounds a halogen light bulb on one side of the optical path from the slit to the lens.
In a slit exposure illumination device, a second reflecting mirror is provided on the opposite side of the first reflecting mirror across this optical path, and the pulp surface of the halogen bulb is illuminated in a slit-like manner on the document surface on the contact glass. The pulp is divided into a belt-shaped frosted surface and a clear surface along the axis, with the pulp surface facing the slit of the halogen bulb and the pulp facing the reflective surface of the first reflecting mirror, which illuminates the slit with the reflected light. The surface part is a frosted surface, and the pulp surface part faces the reflective surface of the first reflecting mirror, and this reflected light passes through the second reflecting mirror to illuminate the slit.This reflected light is returned to the bulb. This device is characterized by arranging a halogen light bulb in such a position that the clear surface forms a part of the pulp surface.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

Figures 3 (a) and (b) show the bulb surface of a halogen light bulb, in this example half of the bulb is frosted, resulting in a structure that is divided into a frosted surface 8 and a clear surface (last frosted surface) 9. (Hereinafter, this light bulb will be referred to as a half-frost type or Rogen light bulb). The light distribution on a plane perpendicular to the tube axis of this Norogen light bulb is non-axisymmetric, as shown in FIG. Therefore, the light distribution characteristics of this halogen bulb in the tube length direction vary depending on the axial direction of the halogen bulb.The frost side has the characteristics of a frost type halogen bulb, and the clear side has the characteristics of a clear type bulb. Each has the characteristics of a Rogen bulb. When this NO-ROGEN light bulb is incorporated into a lighting device, the illuminance and illuminance distribution on the slit surface naturally change significantly depending on the axial direction of the NO-Rogen light bulb.

Figure 5) shows the illuminance distribution on the slit surface when half-cross type halogen bulbs are incorporated into the illumination device shown in Figure 1, and the cross-shaped halogen bulbs are arranged in the positional relationship shown in Figure 6(b). This is what was measured.

Curve A is a clear-type halogen bulb, curved opening is a cross-shaped halogen bulb, and curves No., 2, E, and H are half-frost type? - Illuminance distribution of each rogen bulb. As shown in FIG. 6(b), curve A has the highest illuminance, but the illuminance is highly uneven. The curved opening has extremely little unevenness in illuminance, but the illuminance is about % that of a clear halogen bulb. Curves C, 2, E, and B have illuminance and uneven illumination between those of clear type halogen bulbs and frost type halogen bulbs. Illuminance and illuminance unevenness generally have a contradictory relationship. However, as shown in Figure 5(a), in the case of a half-frost type halogen bulb (curve E), it is possible to obtain a less uneven illuminance distribution similar to that of a frosted halogen bulb without significantly lowering the illuminance. Can be done.

The reason why there is little unevenness in illuminance in the half-frost type solar light bulb (curve E) is thought to be due to the following reasons.

FIG. 6 shows the path of light emitted from the halogen bulb 1 of this lighting device until it reaches the PK. The light that illuminates Fo (Halogen IE)
ff1→P), Fl C halogen bulb 1-first reflecting mirror 2a (AB)→P) tF2 (c.

It consists of three components: electric bulb 1 -> first reflecting mirror 2b (aI) - second reflecting mirror 3 -> P]. Of these, Fo is the direct light from the halogen bulb, and Fl is the primary reflected light, and since the optical path length of these lights from the halogen bulb 1 to Surin) P is short, the illuminance distribution on the slit surface is similar to that of the halogen bulb itself. The characteristics are almost similar to the light distribution characteristics of . In other words, if the slit P of the half-frost-type λ halogen bulb and the bulb surface facing the reflective surface 2a of the first reflecting mirror 2 are clear, the light distribution characteristics will be the same as that of the clear-type halogen bulb; A slit surface illuminance distribution that approximates the light distribution characteristics of a frosted halogen bulb can be obtained.

On the other hand, F2 is light that has been reflected twice by the reflecting surface 2b of the first reflecting mirror 2 and the second reflecting mirror 3; The second reflecting mirror is also not a perfect mirror surface, and when the number of reflections increases, the light is diffused. Also, the optical path length is much longer than Pl. Therefore, the illuminance distribution on the slit surface is similar to the light distribution characteristics of the halogen bulb itself, and the unevenness of illuminance is reduced. Therefore, even if the pulp surface on the side facing the reflecting surface 2b of the first reflecting mirror is clear, the illuminance unevenness on the slit surface is extremely reduced.

It is structurally impossible to direct all of the light from the halogen bulb 1 toward the slit P by the first reflecting mirror 2. For this reason, the shape of the reflecting surface 2c (BC) of the first reflecting mirror, which cannot effectively utilize this reflected light, is usually an arc, and the halogen bulb 1
The light emitted to the reflective surface 2C side returns to the halogen bulb side again.

FIGS. 7(a) and 7(b) show the state of light reflection on this arc-shaped reflecting surface. (a) shows that when the pulp surface on the reflecting surface 2C side is the frosted surface 8, ( b) is the case where the clear surface 9 is also used. In the case of (,), the light emitted from the filament is diffused by passing through the frost surface 8,
Since these lights are further diffused by the reflective surface 2C, only a small amount of the light is returned to the filament 7 or the clear surface 9 side through the frosted surface 8, and therefore does not contribute much to the illuminance of Surin)P.

On the other hand, in the case of (G2), most of the light emitted from the filament 7 is returned to the filament γ side, increasing the brightness of the frosted surface 8. This will increase the illuminance.

The curved line in Figure 5 is partially frosted) The illuminance distribution on the slit surface when the Rogen bulb is used in the arrangement shown in Figure 6, and the illuminance is the clear type X Rogen bulb and the frosted Rogen bulb. However, the unevenness of illuminance was almost the same as that of the frost-type non-rogen bulb.

The frosted surface is obtained by chemically or mechanically roughening the valve surface. It is easiest to process the frosted surface if it is provided on about half of the surface along the tube axis, and in the case of this example, we have described the half-frosted type non-rogen light bulb; however, the frosted surface does not necessarily have to be half-sided. . 1st
For various slit exposure illumination devices with different shapes and sizes of second reflectors, we prototyped NO-ROGEN light bulbs with different proportions of the frosted surface to the entire bulb surface, and determined the slit surface illuminance and illuminance distribution, and the NO-ROGEN light bulbs. As a result of comprehensively examining the effects of misalignment of the mounting position, etc., it was confirmed that the optimal frost surface for each lighting device is in the range of 1A to 2/3 of the total surface of the pulp.

It was also confirmed that even if the positional relationship between the first reflecting mirror and the frosted surface of the partially frosted halogen bulb deviated somewhat from the relationship shown in FIGS. 6 and 7, there was no significant change.

As described in detail, the present invention uses a halogen bulb in which a 70-stroke strip is partially applied to the pulp ground along the tube axis. The halogen light bulb is arranged in a positional relationship in which the pulp surface of the light bulb and the pulp surface on the reflective mirror surface side that illuminates the slit with light reflected by the first reflective mirror are the frosted surface, and the other pulp surface is the clear surface. As a result, it is possible to provide a lighting device for slit exposure that has the features of both clear type halogen light bulbs and 7-day strike type halogen light bulbs, that is, high slit surface illuminance and light distribution characteristics with little unevenness in illuminance.

[Brief explanation of the drawing]

Fig. 1 is a schematic vertical cross-sectional view of a lighting device for slit exposure of a copying machine, Fig. 2(a) is a structural diagram of a non-rogen light bulb for exposure;
Figure 3 (b) is a light distribution characteristic diagram of clear type and frost type halogen bulbs, Figure 3 (, ) is a sectional view showing an example of a half-70 stroke type halogen bulb according to the present invention, and Figure 3 (b) is its main part. The front view and Fig. 4 are diagrams showing the light distribution characteristics of the tube axis and vertical section of this half-frost type halogen bulb, and Fig. 6 (a) shows the clear type and frosted type halogen bulbs, as well as the first reflecting mirror and part. The 6th frosted halogen bulb
A diagram showing the light distribution characteristics in the longitudinal direction of the slit when arranged in the relationship shown in Figure (b), Figure 6 is a diagram showing the path of light from the filament of a halogen light bulb to the slit, Figure 7 (a), (b) is a diagram showing the path of light in the arc portion of the first reflecting mirror, (a) shows the crost surface on the arc side, and (b)
) is a diagram showing the case where the clear surfaces are respectively arranged on the arc sides. DESCRIPTION OF SYMBOLS 1... Halogen light bulb, 2... First reflecting mirror, 3... Second reflecting mirror, 8... Frosted surface, 9... ...Clear surface. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure @ 2 figure hau'f>'1m' 7th term 159th word Qinfu figure 3 (Q/) (b) figure 5 (oJ)
i (mrrn4T3 8 2 ho he Figure 6 (α) (b)

Claims (1)

[Claims] A halogen bulb provided on one side of the optical path from the slit to the lens, a first reflecting mirror having a reflective surface that partially surrounds the halogen bulb, and a first reflecting mirror provided on the opposite side of the first reflecting mirror across the optical path. A lighting device for slit exposure consisting of a second reflecting mirror provided, wherein the halogen bulb has a belt-shaped frosted surface along the tube axis and a clear surface on the pulp surface, and faces the slit. The portion of the pulp surface on the side and the portion of the pulp surface that faces the reflective surface of the first reflective mirror and illuminates the slit with light reflected by this first reflective mirror become the frosted surface, and A portion of the pulp surface facing the reflective surface of the reflecting mirror, through which the reflected light illuminates the slit after passing through the second reflecting mirror, and a portion of the pulp surface where the reflected light is returned to the pulp are clear surfaces. A lighting device for slit exposure, characterized in that the halogen bulb is arranged in a positional relationship such that: