JPH0327095B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides illumination for a slit exposure type copying machine that makes it possible to effectively utilize reflected light from a light source, particularly reflected light from a reflecting mirror located behind the light source. Regarding equipment.

Prior Art FIGS. 1 to 4 show different conventional embodiments.

In each figure, an elliptical reflector 2 with a constant cross-sectional shape
A is placed so that the center of the light source 1A coincides with the first focal point F ₀₁ , but since the original glass 3A has a refractive index greater than 1, the second focal point F ₀₂ is usually a target on the upper surface of the original glass 3A. It is often set a little apart from the focal point P ₀ , and in order to make the illumination width of the document surface more than a certain width, the distance from the target focal point P ₀ to the second focal point F ₀₂ is intended. It may be made larger. Moreover, the light source 1A typically has a diameter of 6
mm or more, and from the viewpoint of machine space and light source performance, there must be a distance of at least 1 mm or more between the reflector and the inner wall of the reflector. Therefore, elliptical reflector 2A
The shortest distance between the first focal point F ₀₁ and the inner surface of the reflecting mirror needs to be at least about 4 mm.

In FIG. 1, the elliptical reflecting mirror 2A is formed by one ellipse 4A, but the angle at which the center of the light source 1A, that is, the first focus F ₀₁ of the ellipse 4A, looks at both ends of the reflecting mirror 2A is the ellipse. This is a different case on both sides of the main axis of 4A. In the case of the reflecting mirror 2A having this shape, all of the reflected light from the reflecting mirror 2A having a smaller viewing angle indicated by the angle ω ₀ behind the light source returns to the light source 1A and attempts to increase the luminous efficiency of the light source 1A. 1
Since the filament of A has a complicated shape,
This causes uneven light source. Furthermore, even if the tube wall of the light source 1A is frosted to reduce light source unevenness, the reflected light beams returned to the light source 1A are diffused by the frosted tube wall and take a complicated path. It is not possible to condense the light to a predetermined position near the target condensing point P ₀ on the original glass 3A and use it effectively.

In Fig. 2, since the angle (α ₀₁ +ω ₀ + α ₀₂ ) at which the center F ₀₁ of the light source 1A looks at the reflecting mirror 2A increases, the eccentricity of the reflecting mirror 2A is closer to 1 than in Fig. 1, and the degree of polarization is This is a case where a large ellipse 5A is adopted. In this case, the shortest distance between the center F ₀₁ of the light source 1A and the reflecting mirror 2A is smaller than the minimum dimension of 4 mm required to install the light source 1A, so the part of the reflecting mirror 2A corresponding to the angle ω ₀ is Unless the arcuate auxiliary reflecting mirror 2B with a large radius is provided, it will be impossible to attach the light source 1A. In other words, when such an arcuate auxiliary reflecting mirror 2B is provided, the angle (α ₀₁ +
α ₀₂ ) will decrease, so in this case as well,
The available angle at which the reflected light beam can be focused at a predetermined position cannot be increased.

FIG. 3 shows that the reflecting mirrors 2A and 2C are
It is formed by a combination of two ellipses 6A and 6B that share the focal points F ₀₁ and F ₀₂ and each hand axis but have different major axis lengths, and the two reflecting mirrors 2A and 2C are connected to the light source 1.
The portions indicated by angles φ ₀₁ and φ ₀₂ with respect to the center F ₀₁ of A are connected by appropriate curved surfaces. When the reflecting surface is formed as described above, the part of the reflecting mirror 2C indicated by the angle (β ₀₁ +β ₀₂ ) can contribute to light collection, but the reflection indicated by the angle ω ₀ at the back of the light source 1A area of mirror 2C, and two reflecting mirrors 2A, 2
The angles φ ₀₁ and φ ₀₂ connecting C cannot be effectively used for condensing light due to vignetting caused by the tube wall of the light source 1A and the like. In this case, the condensing angle of the reflecting surface that can be effectively used is (α ₀₁ +α ₀₂ +β ₀₁ +β ₀₂ ), but the angles β ₀₁ , +β ₀₂ ) are not sufficient due to the constraints of the ellipses 6A and 6B. Therefore, the effective angle of use cannot be increased very much.

In Fig. 4, in order to prevent shadows when a thick original is illuminated, the reflecting mirror 2A is combined with a combination of two ellipses 7A and 7B whose principal axes intersect at the first focal point _F01 , and the light source is A plane reflector 4A is provided that illuminates a part of the reflected light beam from the optical axis of the imaging light from opposite directions across the optical axis of the imaging light. This is a case where P ₀ is illuminated. In this case as well, since the shape of the reflecting mirror 2A behind the light source must be configured as shown in any of the above-mentioned Figures 1 to 3, the reflected light rays are reflected from the part of the reflecting mirror 2A indicated by the angle ω ₀ . Since the reflected light beam is vignetted or diffused by the tube wall of the light source 1A, there is a problem in that the reflected light beam cannot be effectively focused on a predetermined position on the document glass 3A, as in the case of each of the above-mentioned embodiments.

Purpose This invention has been made in view of the above circumstances, and provides a slit exposure type copying machine that can effectively utilize the reflected light from the reflecting mirror behind the light source by focusing it on a predetermined position on the document glass. The object of the present invention is to provide a lighting device.

SUMMARY OF THE INVENTION The present invention provides an illumination device for a slit exposure copying machine that is equipped with a composite reflector that reflects light from a light source onto a slit illumination area through which a document passes, which focuses light from the light source onto the slit illumination area. A virtual line connecting the light source and the slit illumination area among the curves drawn by an ellipse that has a main reflecting mirror that emits light, a first focal point at the light source position, and a second focal point near the end of the main reflecting mirror on the side far from the light source. an auxiliary elliptical reflector formed by a curve on the same axis as the second focal point with respect to the line and provided at the rear side of the back of the light source opposite to the slit illumination area with respect to the light source; and an end of the main reflector on the side far from the light source. The gist of the configuration of the present invention is to provide a composite reflector including a second auxiliary reflector that is provided near the auxiliary reflector and directs the reflected light reflected by the auxiliary reflector to the slit illumination area. be.

Embodiment FIGS. 5 and 6 show a first embodiment of the present invention, in which FIG. 5 is a sectional view of a composite reflecting mirror 2 (hereinafter abbreviated as reflecting mirror 2), and FIG. 6 is a reflecting mirror 2. mirror 2
Each ellipse and other curves forming the inner surface of are shown. The reflecting mirror 2 is formed by combining four types of ellipses and two types of curves, and the two ellipses a ₁ and a ₂ on the end side of the reflecting mirror 2 have a first focus F ₁ and a second focus F _{2 .} are common and have different major axis lengths, but the reflected light from the light source ₁ whose center coincides with the first focal point F1 is focused near the optical convergence point P on the upper surface of the original glass 3 (original the second illumination area)
The focal point _F2 is set at a position close to the focal point P.

Auxiliary elliptical reflector 2 located behind the light source 1
Ellipses a ₃ and a ₄ forming ellipses a and 2b are the first
The focal point F ₁ is common to the first focal point F ₁ of the ellipses a ₁ and a ₂ that form the main reflecting mirror that focuses the light from the light source onto the slit illumination area, and the second focal point F ₃ and F ₄ are the ellipses a ₂ , a ₂ is close to the end far from the light source. Reflector 2
In addition to the auxiliary elliptical reflectors 2a and 2b, a second auxiliary reflector 2c formed by curves _a5 and _a6 is used to direct the reflected light beams from these toward the vicinity of the target focal point _P0 . , 2d are provided to connect the ellipses a ₁ and a ₂ . The curves a ₅ and a ₆ depend on whether the luminous flux is incident on the target focal point P or the target illumination area as a parallel ray or as a convergent ray.
As will be described later, a parabola, circle, ellipse, hyperbola, etc. can be employed.

The angle of each curved surface constituting _the reflecting mirror 2 with respect to _the first focal point F ₁ is as shown in FIG. It's different. The angles γ ₁ and γ ₂ that both ends of the curves a ₅ and a ₆ make with the first focal point F ₁ are set as low as possible because the direct rays from the light source 1 are concentrated in the vicinity of the target focal point P. Set it small.

When the reflecting mirror 2 is configured as described above, the light source 1
The light rays emitted from the ellipses a ₁ and a ₂ are both directed directly toward the second focal point F ₂ and are focused near the target focal point P on the original glass 3 . On the other hand, the auxiliary elliptical reflectors 2a and 2b behind the light source 1
In order to avoid _the inconvenience of vignetting or being diffused by the tube wall _of light source ₁ , _the light _rays reflected at , a ₆ second auxiliary reflecting mirror 2
It is possible to reflect the light again at c and 2d and focus it near the target focus point P. Moreover, since the angles γ ₁ and γ ₂ formed by the curves a ₅ and a ₆ that make it difficult to use direct light rays for condensing can be set sufficiently small, the effective utilization angle for the reflecting mirror 2 that can condense the light to the target condensing point P is , (α ₁ +
α ₂ +α ₃ +α ₄ +β ₁ +β ₂ ), which can be significantly increased.

Figures 7 and 8 show the second
This shows an example. In order to prevent the occurrence of shadows when copying a three-dimensional original, there are six types of ellipses b ₁ , b ₂ , b ₃ , b ₄ , b ₅ , b ₆ and two types of reflecting mirrors. A complementary reflecting mirror 4 (hereinafter abbreviated as reflecting mirror 4) formed by the combination of curves b ₇ and b ₈ of This is a case where the mirror is configured with a plane reflecting mirror 5 that focuses the light on the target light focusing point P of No. 3.

The ellipses b ₁ , b ₃ and ellipses b ₂ , b ₄ of the reflecting mirror 4 have common first and second foci F ₁ , F ₂ and F ₁ , F ₅ respectively, and the second focus F ₅ is located below the original glass 3, and another second focal point _F2 is the target focal point P.
located close to. The reflecting mirror 4 is a main reflecting mirror that has a first focal point F ₁ common to each of the ellipses at the rear of the light source 1, and second focal points F ₃ and F ₄ that condense the light from the light source to the slit illumination area. forming an ellipse
Auxiliary elliptical reflector ₄ consisting of two ellipses b ₅ and b ₆ located close to the ends of b 3 and b 4 on the side far from _the light source
a, 4b, and the second focal point F ₃ ,
Near F ₄ is a second auxiliary reflector 4 that directs the reflected light beams from the auxiliary elliptical reflectors 4a and 4b to the target focal point P either directly or via a plane reflector 5.
c, 4d are ellipses b ₁ and b ₃ and ellipse b ₂ and
B is formed to connect ₄ . It is possible to adopt various curves for the curves b ₇ and b ₈ forming the reflective surfaces of the auxiliary reflecting mirrors 4c and 4d, and to set the angles γ ₁ and γ ₂ formed with respect to the first focal point F ₁ to be as small as possible. The desirability is the same as in the previous embodiment, and the angle formed by each ellipse with respect to the first focal point ₁ is as shown in FIG.

When the reflecting mirror is configured as described above, the light rays emitted from the light source 1 and reflected by the ellipses b ₁ and b ₂ are both directed directly to the second focal point F ₂ and are directed toward the original glass 3.
The light rays are focused near the target focal point P, but are reflected by the ellipses b ₂ and b ₄ on the opposite side. After being reflected by the plane reflecting mirror 5 toward the second focal point F ₅ , the light rays are The image light is focused on the target focal point P from the opposite side of the optical axis. On the other hand, the light beam reflected by the auxiliary elliptical reflector 4a behind the light source 1 is reflected by the auxiliary reflector 4c toward the second focal point _F3 , and then condensed at the target focal point P. The light beam reflected by the auxiliary elliptical reflector 4b is reflected by the auxiliary reflector 4d toward the second focal point _F4 , and then is focused on the target from the opposite side of the optical axis of the imaging light via the plane reflector 5. The light is focused on point P.

Therefore, in this case, the effective utilization angle of the light from the reflecting mirror 4 that can be focused on the target focusing point P is (α ₁ +
α ₂ + α ₃ + α ₄ + β ₁ + β ₂ ), the reflected light beams can be focused from both sides of the optical axis of the imaging light to the target focal point P, eliminating shadows even in three-dimensional originals. No lighting can be done.

9 and 10 show a third embodiment of the reflecting mirror, in which the ellipses b ₁ and b ₂ in the second embodiment are omitted, and the ellipses b 3 and b ₃ forming the main reflecting mirror are omitted. This is a case where the portion b ₄ is enlarged to form ellipses c ₁ and c ₂ , and the plane reflecting mirror 5 is transformed into a plane reflecting mirror 7 composed of two planes. Composite reflector 6
(hereinafter abbreviated as reflector 6), the auxiliary elliptical reflectors 6a and 6b behind the light source are two ellipsoids _c3 having a common first focus _F1 and second foci _F3 and _F4, respectively. , c ₄ , and one of the second auxiliary reflecting mirrors 6c on the end face side emits from the light source 1 and passes through the auxiliary elliptical reflecting mirror 6.
It is formed by a curve c ₅ that directs the light beam reflected by point a to the vicinity of the target focal point P on the original glass 3. On the other hand, the other second auxiliary reflecting mirror 6d directs the reflected light from the auxiliary elliptical reflecting mirror _6b to the first reflecting mirror 7 below the flat reflecting mirror 7 according to the curve c6.
a, and is guided by the ellipse _c2 to the second reflecting mirror 7b above the plane reflecting mirror 7, and the target focus on the original glass 3 from the opposite side of the optical axis of the imaging light. The reflected light beam is focused near the light point P. The angle between each curve of the reflecting mirror 6 and the first focal point _F1 is as shown in FIG.

When the reflecting mirror is configured as described above, the light beam emitted from the light source 1 and reflected in the direction of the second focal point F ₂ by the ellipse c ₁ is directly transmitted from the auxiliary elliptical reflecting mirror 6 a behind the light source to its second focal point. The light rays reflected in the direction of F ₃ are each focused in the vicinity of the target focal point P via the auxiliary reflecting mirror 6c. On the other hand, the opposite ellipse c ₂
A ray of light reflected in the direction of its second focus F ₅ from
Once the auxiliary elliptical reflector 6b behind the light source reaches the second reflector 7b of the plane reflector 7, its second focus F ₄
The reflected light beams are once divided and focused on the first reflecting mirror 7a of the plane reflecting mirror 7 via the auxiliary reflecting mirror 6d, and then focused on the target from the opposite side of the optical axis of the imaging light. The light is focused near point P.

Therefore, in this case as well, as described in the second embodiment, it is possible to improve the efficiency of light use and prevent shadows from appearing even in a three-dimensional original. Moreover, the first and second reflecting mirrors 7a and 7b of the plane reflecting mirror 7 only need to focus the reflected light beams from the ellipse c ₂ and the curve c ₆ separately on the target focal point P. The design of the reflecting mirror 7 can be easily designed to improve the light collection efficiency.

In each of the above embodiments, the light is focused on the target focal point P at the center of the slit width W. However, since the slit width W of a copying machine is usually set in the range of 2 to 20 mm, the slit width W The illuminance distribution in the direction is shown in Figure 11a.
The result will be as shown below. Therefore, in each of the above embodiments, if it is desired to provide as uniform illumination as possible for the set slit width W, it is sufficient to separate the target light condensing point P into a plurality of pieces.

That is, in the first embodiment, the second focal point of the ellipses a ₁ and a ₂
Although F ₂ is common, by setting it at different points, the target light focusing point P can be separated into P' and P'' on the surface of the original glass 3, and the slit width W can be set to 2 to 20 mm. When PP' and PP'' are determined to be within the range of 1 to 10 mm, the combined illuminance distribution curve in the slit width W direction will be as shown by the solid line in FIG. 11b.

In the second embodiment, the common second focus of ellipses b ₁ and b ₃
F ₂ is set at different points, the target focal point P is separated into P' ₁ and P'' ₁ , and the common second focal point of ellipses b ₂ and b ₄ is set.
F ₅ is also set at different points to set the target focal point P to P′ ₂ and P″ ₂
If the light beams are separated into two, the combined illuminance distribution curve in the direction of the slit width W becomes even more uniform, as shown by the solid line in FIG. 11c.

In the third embodiment, for each path of the reflected light rays from the ellipses c ₁ , c ₂ , c ₃ , and c ₄ , the target focal point P is set to P' and P'' by changing the setting angle of the plane reflector 7. If the slit width W is separated, the obtained illuminance distribution curve becomes as shown by the solid line in FIG.

As mentioned above, when the target focal point P is separated into multiple points on the surface of the original glass 3, the separated points
Regardless of the order of P′ and P″ and P′ ₁ , P′ ₂ , P″ ₁ , P″ ₂ , the amount of light proportional to the slit width W can be obtained, making it easy to eliminate uneven illumination of the slit width W. Because it will be,
Even when the slit position is slightly shifted by l as shown in FIG. 11d due to a copying machine setting error, the amount of illumination light within the slit width W can be prevented from changing.

Next, the curved shapes of the auxiliary reflecting surfaces 2c, 2d, 4c, 4d, 6c, and 6d in the first to third embodiments and the condensing characteristics of the reflected light beams to the target illumination area will be explained.

Figures 12 and 13 show the first, second and third
It shows a portion of the reflecting mirrors 2, 4, and 6 common to the embodiments and the optical path of the reflected light beam. L ₁ is the first focal point
The center of the light source ₁ is provided to coincide with F 1, L ₂ is the secondary light source corresponding to the second focus F ₃ or F ₄ of the ellipse in each example, and S ₁ is the auxiliary elliptical reflector behind the light source. ,
S ₂ is a second auxiliary reflecting mirror, and E indicates a target illumination area (near area of P) to which the reflected light beam should go.

FIG. 12 shows a case where the secondary light source L ₂ is inside the reflecting mirror, and the light ray that comes out within the range of angle θ ₁ from the light source L ₁ and reflected by the auxiliary elliptical reflecting mirror S ₁ is the secondary light source L ₂ It converges at an angle θ ₂ , is reflected by the auxiliary reflecting surface S ₂ , and reaches the target illumination area E as a parallel beam or a narrow beam. However, the light beam at the angle φ that is directly incident on the auxiliary reflecting mirror S ₂ from the light source L ₁ may not reach the target illumination area E because it is reflected in the direction shown by the broken line.
Therefore, in order to effectively condense light using the auxiliary elliptical reflecting mirror S ₁ , it is better to make the angle θ ₁ larger and the angle φ smaller. The angle φ is determined by setting the secondary light source L ₂ close to the auxiliary reflector S ₂ or setting the auxiliary reflector S ₂ close to the light source L ₁
It can be made smaller if it is placed away from it.

When the auxiliary reflecting mirror _S2 is a parabola, and the secondary light source _L2 is the focus of the parabola, the luminous flux f of the reflected light beam becomes a parallel light beam and enters the target illumination area E. When the auxiliary reflector S ₂ is elliptical, the secondary light source L ₂ is its first focus,
When the second focal point is set in the direction of the target illumination area E, the light flux f enters the target illumination area E while converging. When the auxiliary reflecting mirror _S2 is a circle, the light flux f can be made into a parallel light beam or a convergent light beam by setting the center position and radius to appropriate values. In this case, when the angle θ ₂ is small, for example 30° or less,
Since the aberration is negligible, the auxiliary reflector S ₂
Making it a circle not only simplifies the design but also facilitates manufacturing, which is very advantageous in practice.

Figure 13 shows the apparent secondary light source (imaginary light source) L ₂
is outside the reflector.

If the auxiliary reflector S ₂ is a parabola, its focal point is L ₂ ,
When the parabolic axis is set to point from _L2 toward the target illumination area E, the light flux f becomes a parallel ray that enters the target illumination area E. When the auxiliary reflector S ₂ is a hyperbola convex inward, and the first focal point is L ₂ , the luminous flux f
Since it converges on the second focal point, the light flux f can be incident on the target illumination area E. When the auxiliary reflecting mirror S ₂ is a circle, the light flux f can be a parallel light beam or a converging light flux, as described with reference to FIG.

When a circle is used as the auxiliary reflecting mirror _S2 , the size of the radius r and the center position may be determined as follows.

If you want to make parallel rays of light enter the target illumination area E, if you determine the angle, dimensions, etc. as shown in Figure 14, the center O of the circle will be located on the bisector of ∠L ₂ ME ₀ , And it may be set at a position γ=2x/cosθ (1) from the center M of the auxiliary reflecting mirror S ₂ . Here, E ₀ is the center of the target illumination area E, and δ is a small angle.

If you want to make a convergent light beam enter the target illumination area E, the center O of the circle in Fig. 15 is ∠
Located on the bisector of L ₂ ML ₃ , and with an auxiliary reflector
It may be set at a position r=2/(1/X ₁ +1/X ₂ )cosθ (2) from the center M of S ₂ . Here, L ₃ is the convergence point of the convergent light beam, the straight line ML ₃ passes through the target illumination area E, and δ is a small angle. If L ₃ is set at the center E ₀ of the target illumination area E, the reflected light beam can be focused on E ₀ , and by setting L ₃ at a position away from E ₀ on the straight line ME ₀ , the reflected light beam can be focused on the target illumination area E. The illumination width in the illumination area E can be adjusted freely to some extent.

The above equations (1) and (2) are expressed as a virtual light source L ₂ as shown in FIG.
When applied _{to the} auxiliary reflector _{S 2 of} The positive and negative numbers indicate that the circle forming the auxiliary reflector _S2 is concave or convex inside the reflector, respectively.

The present invention is not limited to each of the above embodiments, but has either the upper half or the lower half of the synthetic reflector of each embodiment take the form of this embodiment,
Of course, the other half may be combined in the form shown in FIGS. 1 to 4 shown in the prior art section.

Effects This invention provides an illumination device for a slit exposure type copying machine that is equipped with a composite reflector that reflects light from a light source onto a slit illumination area through which a document passes, and which focuses the light from the light source onto the slit illumination area. A virtual line connecting the light source and the slit illumination area among the curves drawn by an ellipse that has a main reflecting mirror that emits light, a first focal point at the light source position, and a second focal point near the end of the main reflecting mirror on the side far from the light source. an auxiliary elliptical reflector formed by a curve on the same axis as the second focal point with respect to the line and provided on the rear side of the light source opposite to the slit illumination area with respect to the light source; and an end of the main reflector on the side far from the light source. A second auxiliary reflector is provided near the auxiliary reflector and directs the light reflected by the auxiliary reflector to the slit illumination area. The light reflected by the mirror enters the slit illumination area without being eclipsed or diffused by the light source, and can be used effectively.

[Brief explanation of drawings]

1 to 4 are cross-sectional views of reflecting mirrors showing different conventional embodiments, and FIGS.
The figure is a cross-sectional view of a reflecting mirror and its constituent curve group showing a first embodiment of the present invention, and FIGS. 7 and 8 are a cross-sectional view of a reflecting mirror and its constituent curve group according to a second embodiment.
FIGS. 9 and 10 are a cross-sectional view of the reflecting mirror and its constituent curves for the third embodiment, and FIGS. 11a, b,
c is an illuminance distribution curve when there is one target focal point and when there are multiple target focal points, d is a diagram showing the relationship between the slit and the deviation of the illumination position when there are multiple target focal points,
12 and 13 are reflection path diagrams showing the reflection characteristics of the auxiliary reflection surface, and FIGS. 14 and 15 are diagrams showing how to determine the center position and radius when the auxiliary reflection surface is a circle. 1... Light source, 2, 4, 6... (composite) reflecting mirror,
2a, 2b, 4a, 4b, 6a, 6b...auxiliary elliptical reflector, 2c, 2d, 4c, 4d, 6c, 6d
... Second auxiliary reflecting mirror, a ₂ , b ₃ , b ₄ , c ₁ , c ₂ ...
Curve forming the main reflecting mirror, E...slit illumination area.

Claims (1)

[Scope of Claims] 1. An illumination device for a slit exposure type copying machine equipped with a composite reflector that reflects light from a light source onto a slit illumination area through which a document passes, comprising: A main reflecting mirror that focuses light on the light source, and a curve drawn by an ellipse that has a first focal point at the light source position and a second focal point near the end of the main reflecting mirror on the side far from the light source, between the light source and the slit illumination area. an auxiliary elliptical reflector formed by a curved line on the same side as the second focal point with respect to the connecting imaginary line and provided behind the light source on the opposite side to the slit illumination area with respect to the light source; and a side of the main reflector far from the light source. A slit exposure type copying machine comprising a second auxiliary reflecting mirror provided near an end of the auxiliary reflecting mirror to direct the reflected light reflected by the auxiliary reflecting mirror to a slit illumination area. lighting equipment.