JPS5848829Y2 - slit lighting device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an illumination device for adjusting the illumination distribution in an illumination section when illuminating a document surface in a slit shape in a facsimile document reading device or a copying machine.

In facsimile document reading devices and slit exposure type copying machines, the surface of the document is generally illuminated in a slit shape.
The imaging optical system forms an image from the illumination unit onto the light-receiving area of the solid-state sensor or onto the photoreceptor, but in order for the information on the document to be read correctly or for a good latent image to be formed, it is necessary to The light intensity distribution of the slit-shaped image on the imaging plane is
In addition to uniformity in the longitudinal direction of the slits, it is desired to improve the lighting efficiency in order to save power and to avoid an abnormal rise in temperature inside the main body.

Conventionally, as a means for improving illumination efficiency, in a lighting device using a linear light source having an intermittent light emitting part such as a halogen lamp, as shown in FIG. A linear light source 1 is installed at the focal point of
are fixed to both sides of the lighting device.

Since this planar reflector configuration was applied only to the peripheral light emitting parts, the total light emission length as a whole tended to be long.
Therefore, problems such as an increase in the total power consumption of the light source and an abnormal rise in temperature have occurred.

Furthermore, by using a light source with intermittent light emitting parts and arranging the light emitting parts appropriately, it is possible to provide illumination that corrects the peripheral dimming of the imaging optical system, but each light emitting part is subdivided. This has the disadvantage that the arrangement of the light emitting section for performing the illumination is complicated.

FIG. 2a shows a longitudinal section of the conventional example shown in FIG.
□, lk, In indicate the light emitting part of the linear light source 1, 1
11, In+ is the peripheral light tip 1. ,1. It shows an imaginary light source.

The curve shown in Figure 2 shows the relative illuminance corresponding to the position of the document surface in the case of Figure 2a. Although the effect of improving the relative illumination around the document surface is recognized, the overall illumination efficiency is The improvement is only slight, and it is difficult to make the improvement substantially uniform in the length direction of the illumination section, that is, in the length direction of the slit.

In view of the current situation, when the purpose is to improve lighting efficiency and reduce the power consumption of the light source, it is recommended to use a regular reflector that is approximately perpendicular to the longitudinal direction of the light source and with the individual light emitting parts placed between them. It is conceivable to provide a plurality of plane reflectors with different characteristics, but simply providing a plurality of plane reflectors may improve the illumination efficiency in the length direction of the illumination section, but the illuminance at both ends will decrease. It tends to decrease relatively.

An object of the present invention is to provide a slit-shaped illumination device that can reduce the power consumption of a light source while eliminating peripheral dimming and improving illumination efficiency.

This purpose is to gradually increase the height from the center to both ends in the longitudinal direction of the linear light source, so that the individual light emitting parts are placed between each other and approximately perpendicular to the longitudinal direction of the linear light source. This is achieved by a device comprising a plurality of planar reflectors with large, specular reflection properties.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In FIG. 3, symbols 1□, lk', and In are linear light sources 1
3□, 3k, and 3n indicate flat reflecting plates.

The suffix n indicates the total number, and k indicates an arbitrary number, but in this figure, six planar reflectors are fixedly supported by the cylindrical quadratic curved reflector 2.

The individual planar reflectors 3 are arranged substantially perpendicularly to the linear light source 1, and two adjacent planar reflectors are arranged such that one light emitting section is always placed between them.

Planar reflector 3□, ......, 3, ......
3n in the length direction of the light source 1,
The parts provided at both ends are set to be gradually larger than those provided at the center.

In the case of the illustrated example, the same 3. +1 height 11 are equal to each other, but
The heights 12 of the plane reflecting plate 32 and the height 12 of the same 3°-1 are equal to each other, and the heights 13 of the plane reflecting plate 31 and the plane 3n at both ends are equal to each other.

That is, the height of the plane reflector is set to be gradually larger toward both ends than the center, as in 11<12<13.

Further, the light source 1 is installed at the focal point of a cylindrical quadratic curved reflector.

The symbols x, y, and z in the figure indicate the coordinates with the center of the light source as the origin. Figure 4 shows the xy cross section of Figure 3, and the light source 1 has a quadratic curved reflector as an ellipse. Its first focus O
, the reflected light beams gather at the second focal point P due to the elliptical nature.

The document surface 4a is close to this focus P and between the parfocals P and O.
is configured to intervene.

FIG. 5 shows the Xz cross section of FIG. 3, and +1 is arranged on the plane reflecting plate 3, sandwiching an arbitrary light emitting part 1k.

In this cross section, the law of specular reflection holds, and the light emitting part 1
The light beam diverges from a point Q on the plane reflection plate 3. If we consider that the light is reflected by and reaches the point R on the document surface 4a, it is observed as if it were reflected from the imaginary light source 1kl at 1, according to the law of specular reflection.

Considering this for all the light beams directed to the light emitting section 1k, 3. When +1 is installed, the illuminance distribution on the document surface is as shown in Figure 6.The relative illuminance when there is no flat reflector is only slightly higher at the center position of the document surface as shown in the curved line bt. However, when flat reflectors are installed on both sides of the light emitting part, the relative illuminance increases as shown by Ct at the central position as shown by curve C, and rapidly decreases as it deviates from the central position.

In other words, the directivity increases, and it appears as if the brightness at the main light emitting part is increasing.

We will now explain this in more detail using equations.

FIG. 7 is an explanatory diagram of a part of the diverging light beam from an arbitrary light emitting part in the xz section of FIG. The light then reaches a point B on the document surface 4a (not shown in this figure but shown in FIG. 8), but does not contribute to the illumination of the range Le of the effective document surface.

On the other hand, when the plane reflector 3 has 3b + 1,
According to the law of specular reflection, the above reflected light flux is reflected by the flat reflector 3.
1 reaches point Aa on the document surface 4a at an angle of θ with respect to the X direction.

FIG. 8 shows the coordinates of each point in FIG. 7.

θ is the same in FIGS. 7 and 8.

Planar reflector 3. . 3. The difference AaBa in the illumination width between when +1 is present and when it is not is as follows: The coordinates of points A and H are (z
A, XA).

(z8.XB), so AaBb = l z A
Obtain a-Z Bbl.

From the bottom 2b of the quadratic curved reflector (see Figure 4) to the original surface 4
If the distance to a is L, then BbBa=lzBa−ZB
It becomes b.

becomes.

Reference numeral E indicates the end of the range Le of the effective document surface.

And a flat reflector lk so that AaBa≧EBa,
When +1 is set to 1, the luminous flux that did not contribute to the illumination of the effective document surface in the conventional illumination method contributes, and the illumination efficiency improves.

The above is an explanation for the arbitrary light emitting section 1k, but by determining the size of the plane reflector from each light emitting section 1□ to 1° using the above formula, the illuminance distribution d shown in Fig. 9 can be obtained. It is known that the illuminance distribution is higher in illumination efficiency than the illuminance distribution C in the conventional example.

Furthermore, in this case, it becomes possible to easily correct peripheral light attenuation caused by the imaging optical system and the like.

In this way, by appropriately determining the size of 30,3°...3n-1,3n, it is possible to arbitrarily change the illuminance distribution on the effective document surface, thereby correcting the vignetting caused by the imaging optical system. It can also be easily done.

Although peripheral dimming can be corrected by appropriately arranging the light-emitting parts, the present invention has the effect of increasing the apparent brightness of each light-emitting part by using a flat reflector, which improves the lighting efficiency as a whole. increases, and therefore it becomes possible to reduce the total number of light emitting sections, and the power consumption of the light source can be reduced.

[Brief explanation of drawings]

Figure 1 is a perspective view of the conventional example, Figure 2a is a longitudinal section of Figure 1,
Figure 2 is a diagram of illuminance distribution curve on the document surface according to the conventional example, Figure 3 is a perspective view of the embodiment of the present invention, Figure 4 is an xy cross-sectional view of Figure 3, and Figure 5 is a part of Figure 3. X2 sectional view, FIG. 6 is a document surface illuminance distribution curve diagram explaining the effect of the flat reflector shown in FIG. 5, FIG. 7 is a diagram explaining reflected light flux in the same arrangement as FIG.
FIG. 8 is a diagram showing the coordinates of each point shown in FIG. 7, FIG. 9 is a document surface illuminance distribution curve diagram showing the effect of the present invention, and FIG. 10 is an xz sectional view of FIG. 3. 1... Linear light source, 2... Cylindrical quadratic curved reflector, 3, 3□, 3k, 3n...
...Flat reflector.

Claims (1)

[Scope of utility model registration request] In an illumination method that illuminates a document surface in a slit shape using a linear light source having intermittent light emitting parts and a dinontrical quadratic curved reflector so as to emit diffused light with substantially uniform intensity in the longitudinal direction, The linear light source is arranged substantially perpendicularly to the longitudinal direction of the linear light source, with the individual light emitting parts being placed between them, and the height gradually increases from the center to both ends in the longitudinal direction of the linear light source. A Surin 1-shaped illumination device comprising a plurality of flat reflectors having specular reflection characteristics.