JPS5836466B2 - Halogen lamp - Google Patents

Description

[Detailed description of the invention] The present invention relates to a document illumination light source.

2. Description of the Related Art It is known that an elongated tubular halogen lamp and a light focusing member are used as a light source for illuminating a document in a document reading unit in a facsimile transmitting device, a copying machine, or the like.

FIG. 1 shows an example of such a document illumination light source.

In the figure, numeral 1 is a halogen lamp, numeral 2 is an elliptical reflector as a light focusing member, numeral 3 is a contact glass,
are shown respectively.

As shown in FIG. 2, the halogen lamp 1 has an elongated tubular shape, and has a light emitting line L extending in the longitudinal direction of a quartz tube 1a.

On the light emitting line L, there are a plurality of light emitting parts L1 + L2 + L
3 + L+ is deployed.

The light emitting parts L1, L2, L3, L4 are formed by winding a filament around a coil, and when the light emitting line L is energized, these light emitting parts L1, L2, Ls, L4 emit light.

The number, size, position, etc. of the light emitting parts in a halogen lamp are determined according to the light distribution characteristics required in the illuminated area. Therefore, if the light distribution characteristics change, the number of light emitting parts, etc. will also change. Needless to say, there are scales.

Now, returning to FIG. 1, the elliptical reflecting mirror 2 is a kind of concave mirror whose longitudinal direction is perpendicular to the drawing, and the cross-sectional shape of the mirror surface matches a part of the ellipse EA. .

In other words, the mirror surface of the elliptical reflecting mirror 2 is the ellipse Et in FIG.
The bottom shape corresponds to the circumferential surface of an elliptical cylinder whose axial direction is the tS direction perpendicular to the drawing.

The shape of any cross section of this elliptical cylinder corresponds to the circle Et, and the straight line obtained by extending the focal point of this ellipse Et in the axial direction of the elliptical cylinder is called the focal line, and this is 1st
In the figure, it is indicated by q1q2.

The halogen lamp 1 is arranged so that its emission line L coincides with the focal line q1.

Therefore, in FIG. 1, when the halogen lamp 1 is made to emit light, a part of the light emitted from the halogen lamp 1, that is, the light reflected by the elliptical reflector 2, is directed onto the other focal line q2 in a straight line. converge in a shape.

Therefore, if the document O to be illuminated is fed in the direction of the arrow as shown in FIG. 1, the portion of the document passing over the contact glass 3 will have a width h
The slit shape is illuminated by the reflected light flux.

Figure 3 shows the relationship between the light distribution characteristics in the slit-shaped illuminated area and the illumination light intensity distribution in the illuminated area by the individual light emitting parts. It corresponds to the longitudinal direction of the section.

Light emitting part L1 of halogen lamp 1. L2, L3, L,
In the longitudinal direction of the illuminated length, light intensity distributions P1, P2, P
3 and P4, the light distribution characteristic P is obtained by superimposing them.

Actually, first, a light distribution characteristic P is given, and a light intensity distribution P1 etc. that gives such a light distribution characteristic is also determined, and the light emitting parts L, etc. are determined so as to obtain such a light intensity distribution. The amount of light emitted and the arrangement are designed.

Note that the area indicated by the symbol R is an effective illumination area.

By the way, as shown in FIG. 4, the contact glass 3 is
When placed extremely close to the focal line q2, the width of the slit-shaped illuminated portion becomes extremely narrow.

When the width of this narrow illuminated portion becomes less than about 3 cm, the following problems occur.

That is, as shown in FIG. 5, a curve P represents the light distribution characteristic of the extremely narrow slit-shaped illuminated portion as described above.

Even if the size and arrangement of the light emitting parts L1, L2, L3, L of the halogen lamp 1 are designed accordingly, the light distribution characteristic actually obtained is curve P.

The result will not be smooth and smooth, but rather uneven, like the curve PR.

Such irregularities on the light distribution characteristic curve PR, that is, unevenness in illuminance, are referred to as short-period unevenness in illuminance.

The term "short period" means that the period of unevenness of this uneven illuminance corresponds to the designed light distribution characteristic curve P.

This is because it is shorter than the period of the illuminance distribution in .

Such short-cycle illuminance unevenness occurs when the width of the slit-shaped area to be illuminated by a portion of the light from the halogen lamp is narrowed down to an extremely narrow illumination mode as shown in Figure 4. This can adversely affect reading and copying.

An object of the present invention is to provide a document illumination light source that can effectively reduce such short-cycle illuminance unevenness.

The original illumination light source according to the present invention is characterized by the structure of each light emitting part of the halogen lamp that constitutes the light source.

As described above, the light emitting section of a halogen lamp has a coil structure, and the amount of light emitted by each individual, the position, the number of light emitting sections, etc. are determined according to the light distribution characteristics required in the illuminated section.

In the halogen lamp of the document illumination light source according to the present invention, the amount of light emitted and the arrangement position of each light emitting section are determined according to the light distribution characteristics.

This light distribution characteristic is a design requirement for an extremely narrow slit-shaped illuminated area.

Now, in the present invention, the coils of the individual light emitting parts are shaped into a cylinder, a barrel, or a string.

Here, the shape of the coil refers to the envelope shape of the coil.

When the light emitting section is cylindrical, the pitch of the coil is varied within the light emitting section.

When the light-emitting section is shaped like a barrel or a string, the winding diameter of the coil is changed within the light-emitting section.

The pitch change and the winding diameter change are such that in each light emitting section, the proportion of the coil portion closer to the illuminated portion shielding the coil portion farther from the illuminated portion is averaged in the longitudinal direction of the illuminated portion. It is determined as follows.

Here, the coil portion closer to the illuminated portion and the coil portion farther from the illuminated portion refer to the portion closer to the illuminated portion and the portion farthest from the illuminated portion via the light focusing member.

For example, in FIG. 4, if we consider the coil shape of the light emitting part on the focal line q1, in the coil shape, the side facing the reflecting mirror 2 is the illuminated part (close to the focal line q2). There is.

) is the closest side, and the opposite side is the far side.

By the way, how does the short-cycle illuminance unevenness that has become a problem occur?

As mentioned above, the light distribution characteristic is the superposition of the light intensity distribution in the illuminated area by the individual light emitting parts, and the light intensity distribution is determined according to the light distribution characteristic. The purpose was to form a light emitting part that provided a light intensity distribution.

However, the light intensity distribution of the illuminated area is curve 6- in FIG.
When an extremely narrow area is actually focused and illuminated using a light focusing member using a light emitting portion Li formed to have a width of 1, the actual light intensity distribution will be as shown by curve 6- in FIG. This results in something like 2.

Here, the code Li is the code L, , L2, L3,
This indicates any one of the light emitting parts indicated by L, and will be described below. This example shall be followed.

In this way, the light intensity distribution of each light emitting part Li does not give the curve 6-1 as designed, but gives the curve 6-2, so as shown in FIG. Actual light intensity distribution of L1, L2, L3, L4 7-
1. 7-2. 7-3. Due to the superposition of 7-4, the actual light distribution characteristic is a curve P with short period illuminance unevenness.
This results in an R.

As I repeat, short-period unevenness in illuminance can be caused by using a light focusing member to direct some of the light from the halogen lamp.
This problem is peculiar to the case where the illuminated part is illuminated with extremely narrow condensed light, and if the width of the slit-shaped illuminated part is about 5 mm or more, such a problem will not occur.

That is, if the width of the illuminated part is large to some extent, the light intensity distribution in the illuminated part will be as designed.

Then, what is the reason why the light intensity distribution in the illuminated part does not give the distribution 6-1 in Fig. 6 but gives the distribution 6-2?The reason lies in the coil structure in the light-emitting part Li. It can be said that.

In FIG. 8, symbols C1 to C,1 represent light emitting parts Li.
The figure shows the state of the coil end face on a longitudinal cross section of the coil that constitutes the coil.

In other words, the coils constituting the light emitting part Li are C1 to C2.
, from C2 to C3 until C11.

Note that this figure is an explanatory diagram, and the structure of the coil is also shown in a simplified manner.

In an actual halogen lamp, the number of turns of the coil constituting the light emitting section is about several tens.

In FIG. 8, a straight line 8-1 indicates an extremely narrow slit-shaped illuminated portion.

Then, in this explanatory diagram, C1y C3 t C5
t C7 + Co IcII is the coil portion of the light emitting part Li on the side closer to the illuminated part, and C2 t C4
t Cor C to is the coil portion on the far side from the illuminated part.

Now, if we ignore the coil structure of the light emitting part Li and consider this light emitting part Li as a linear light source having a uniform linear emission density, the light intensity distribution in the illuminated part will be as shown by curve 8-2.

However, when the coil structure is considered, the situation becomes different.

That is, now considering the area D-1 on the illuminated part 8-1, the coil portion CI + C3 g C5 + on the side closer to the illuminated part contributes to the illumination of the temple area D-1.
C7 + Cgs Ctt, and the coil portion C2 on the side far from the illuminated part? C4? C6 1 CB +
CIO is coil part c3j C5 t c7+ C9
It will be shielded by pCl1.

All parts of the coil constituting the light emitting part Li emit light uniformly, but in area D-1, the coil parts C2 and C4 are shielded by the coil part closer to the illuminated part. ,C. , C8, C1.

cannot effectively contribute to the illumination of this area D-1.

Therefore, the light intensity in the region D-1 is lower than the designed one.

The same thing occurs in the regions D-2, D-3, and D-4, and the actual light intensity distribution has irregularities as shown by the curve 8-3.

As mentioned above, such irregularities in the light intensity distribution cause short-period illuminance unevenness in the light distribution characteristics.

Therefore, in order to reduce short-period illuminance unevenness, it is only necessary to reduce the unevenness of the light intensity distribution caused by the individual light emitting parts, which is the cause thereof.

Therefore, in order to see how to reduce the unevenness of the light intensity distribution due to each light emitting part, we took the above consideration one step further, and found that the unevenness in the coil structure of the light emitting part is
When considering what factors are responsible for this, as can be seen from FIG. 8, the cause of the above-mentioned unevenness is that the winding diameter and pitch of the coil constituting the light emitting section Li are constant.

In other words, if the winding diameter and pitch of the coil are constant,
As shown in FIG. 9, the coil portion C2HC4+C6+CatCto on the side far from the illuminated part is connected to the coil portion C. , C3, etc., at specific angles θ,, θ2
This occurs strongly in the direction of , and this forms a noticeable concave portion in the light intensity distribution.

In other words, in such a case, the coil portions C1 and C3
The shielding of the coil portions C2, C4, etc. due to the angles θ1, θ2, etc. is concentrated in specific directions such as angles θ1, θ2, etc.

As long as the light emitting section has a coil structure, it is inevitable that a certain coil section will shield the coil section of the pond.

However, it is possible to avoid concentration of the above-mentioned shielding in a specific direction by making adjustments to the shape, pitch, etc. of the coils.

FIG. 10 is an explanatory diagram showing a coil structure of a light emitting part of a halogen lamp in an embodiment of the present invention.

Since there is no possibility of confusion, the same reference numerals as before will be used for the coil section, as for the light emitting section.

Coil parts C, C3, etc. with odd number suffixes are the coil parts on the side closer to the illuminated part, and coil parts with even number suffixes, such as C2, C4, etc. are the coil parts on the side far from the illuminated part. It is a part.

In this embodiment, the coil of the light emitting part Li has a cylindrical shape, and the pitch changes within the coil.

By changing the pitch of the coil in this way, for example,
The direction of the angle θ3 where the coil portion C3 shields the coil portion C2, the direction of the angle θ4 where the coil portion C5 shields C4, and the direction of the angle θ5 where the coil portion C7 shields C6 are different directions. .

Therefore, in the direction of angle θ3, coil portion C2 is C3
However, coil portions C4, C6, etc. are not shielded by coil portions C5, C7, etc., and thus coil portions C4, 06, etc. may contribute to the illumination in the direction of angle θ3.

In other words, the shielding of the coil portion on the far side by the coil portion on the side closer to the illuminated portion is prevented from concentrating in a specific direction.

In other words, if you place your eyes at the position of the illuminated part, look at the light emitting part Li through the light focusing member, and change the position of your eyes in the longitudinal direction of the illuminated part, you can see from any position. , the number of far-side coil sections that are shielded by the near-side coil sections is approximately constant.

This means that in each light emitting section, the proportion of the coil portion closer to the illuminated portion shielding the coil portion farther from the illuminated portion is averaged in the longitudinal direction of the illuminated portion.

FIG. 11 is an explanatory diagram of an embodiment of the pond, and in this embodiment, the light emitting portion Li has a sag-like shape in the shape of a beer pot.

FIG. 12 is an explanatory diagram of still another embodiment, and in this embodiment, the light emitting portion Li has a lattice shape.

In these examples as well, the coil portions with odd suffixes, such as C1 and C3, are the coil portions closer to the illuminated portion.

In these examples, θ6\θ7ξθ8, θ9\θ, 0
ξθ, 1, etc., and in these examples as well, the col part C
,,C3,C5...etc. coil parts C2,C,,
Concentration of shielding such as C6, etc. in a specific direction is avoided.

Thus, according to the document illumination light source according to the present invention, it is possible to effectively reduce irregularities in the light intensity distribution due to the individual light emitting parts, and therefore it is possible to effectively reduce short-period unevenness in illuminance.

[Brief explanation of the drawing]

Fig. 1 is an explanatory side view showing a conventionally known document illumination light source, Fig. 2 is a front view showing an example of a halogen lamp, and Fig. 3 shows the light distribution characteristics of a halogen lamp. , a diagram for explaining the relationship between light intensity distributions of individual light emitting parts, 4th
9 to 9 are diagrams for explaining short-period illuminance unevenness and its causes, and FIG. 10 is a diagram for explaining one embodiment of the present invention using the coil structure of the light emitting part, which is a special feature thereof. 11 are diagrams for explaining the embodiment of the pond of the present invention by the coil structure of the light emitting part, which is its characteristic part,
FIG. 12 is a diagram for explaining another embodiment of the present invention in terms of the coil structure of the light emitting part, which is a characteristic part thereof. 1...Halogen lamp, 2...Elliptical reflecting mirror as a light focusing member, 3...Contact glass, O...Original, L1 g L2, L3
, J, 4, 'I, i... Light emitting part, C1
, C3, C5, . . . Coil portions closer to the illuminated portion, C2, C4, C6, . . . Coil portions farther from the illuminated portion.

Claims (1)

[Scope of Claims] 1. Disposed parallel to the illuminated portion of the document and at a certain distance from the illuminated portion. an elongated, tubular halogen lamp; and a light focusing member disposed along the halogen lamp to focus a part of the light emitted from the halogen lamp onto the illuminated area in the form of an extremely narrow slit. The halogen lamp has a plurality of light emitting parts in the longitudinal direction of the lamp, each of which has a predetermined arrangement and amount of light emitted according to a desired light distribution characteristic in the longitudinal direction of the illuminated part, Each of the light-emitting parts has a coil structure, and in each light-emitting part, the proportion of the coil part closer to the illuminated part blocking the coil part farther from the illuminated part is averaged in the longitudinal direction of the illuminated part. Either the pitch of the coil of each light emitting part is changed within each coil so that the shape of each coil is cylindrical, or the winding diameter of the coil of each light emitting part is changed within each coil. A document illumination light source characterized in that the shape of each coil is changed to a beer barrel shape or a string shape.