JPH05199366A - Original lighting device for original reader - Google Patents

Abstract

(57) [Abstract] [Purpose] The original to be read is illuminated in the shape of a slit that is long in the main scanning direction, and the image of the illuminated portion by the imaging lens is mainly reflected by the roof-shaped mirror with the optical axis of the imaging lens as the boundary. In an original reading device that divides the image in two in the scanning direction and forms the divided images on separate line sensors, and combines the outputs of the line sensors into a signal in the main scanning direction, the divided images read by each line sensor. Effectively reduces the decrease in the S / N ratio of the signal at the seam. By forming an opening 18A in the central portion of the light shielding means 18 in the main scanning corresponding direction, the vicinity of the intersection of the reading illumination part and the optical axis of the imaging lens is reflected by the reflection means 14, 16 and the tubular shape. The opening 18A in the light-shielding means 18 is provided so as to illuminate with the direct light from the lamp 12 and to realize a desired shading shape in the document reading section.
Adjust the shape and size of.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document illuminating device in a document reading device.

[0002]

2. Description of the Related Art A document reading apparatus which forms a document image on a line sensor and reads the document image has been widely known in the past in relation to a digital copying machine, a facsimile machine and the like. In the line sensor, minute light receiving elements are closely arranged, and a document area in which one light receiving element is converted into a signal at one time is a "pixel".

"High resolution of document reading" means that the size of a pixel signalized as one unit of document information is small. Therefore, in order to read a document with high resolution, the light receiving element in the line sensor is used. The larger the number, the more advantageous it is, but as long as the existing line sensor is used, the limit of resolution is determined by the number of light receiving elements unique to the line sensor.

As a suggestion of a reading method for reading an image exceeding the limit of resolution as described above, Japanese Utility Model Laid-Open No. 63-
There is an imaging device disclosed in Japanese Patent No. 131465. This image pickup device is a device for converting a video image into a signal by using two area sensors, and an application of this technique for reading an original using a line sensor is as shown in FIG. 8 as an explanatory view.

In FIG. 8, reference numeral OI indicates an original image. The direction of the arrow representing the original image OI (the vertical direction in the drawing) is the main scanning direction (corresponding to the arrangement direction of the light receiving elements in the line sensor). Reference numeral 1 indicates an imaging lens. The roof type mirror indicated by reference numeral 3 has two reflecting surfaces 3
A and 3B are combined in a roof shape, and the ridge line portion due to the intersection of the reflecting surfaces 3A and 3B is the optical axis A of the imaging lens 1.
It is located on X, the ridge G corresponds to the main scanning direction orthogonally, and the reflecting surfaces 3A and 3B are arranged symmetrically with respect to the optical axis AX.

The image-forming light beam from the image-forming lens 1 is divided into two by the roof-type mirror 3 in the main scanning direction with the optical axis AX of the image-forming lens 1 as a boundary. One of the divided image-forming light beams is reflected by the reflecting surface 3A, and an image of half of the original image OI (a portion above the optical axis AX in FIG. 8) is formed on the line sensor 4A. The other of the divided image-forming light fluxes is reflected by the reflecting surface 3B and is reflected by the optical axis A of the original image OI.
An image of the lower half of X is formed on the line sensor 4B. In other words, in this document reading method, the “imaging lens 1
The image of the original document image OI is divided by the roof mirror 3 into two in the main scanning direction with the optical axis AX of the imaging lens 1 as a boundary, and the divided images are respectively separated by line sensors 4A and 4B.
It will be imaged on top ". In FIG. 8, the image forming magnification by the image forming lens 1 is shown to be equal for the sake of simplification of the drawing, but the image forming magnification by the image forming lens 1 is generally a reduction magnification.

In this way, each line sensor 4A, 4
Signals corresponding to one line of the original image can be obtained by converting each divided image into a signal by B and combining the obtained signals in series. To read the entire original image two-dimensionally, sub-scanning may be performed in the sub-scanning direction (direction orthogonal to the drawing in FIG. 8), for example, by "sending the original".

Obviously, in such a document reading system, reading can be performed with twice the resolution as compared with the case where one line sensor is used.

By the way, generally, when the document reading illumination unit has a uniform illuminance distribution in the main scanning direction, the brightness of the image formed on the line sensor is determined by the cosine fourth law of the image forming lens or the like. Due to the characteristics of the apparatus, the brightness of the optical axis position of the imaging lens is maximized, and the brightness gradually decreases as the distance from the optical axis increases. Therefore, in general, the document reading unit is illuminated so that the illuminance is large at both ends in the main scanning direction and the illuminance is low at the center (the shape of the illuminance distribution in the reading illuminating unit in the main scanning direction is called a shading shape). .. However, in general, the brightness of the image on the line sensor has a positional variation due to "illumination unevenness" and so on.To correct the variation of the output signal due to such a positional variation of the brightness, It is known that "shading correction" is performed.

By the way, in the above-mentioned "reading an original using two line sensors" reading method, the optical axis ray of the imaging lens 1 is incident on the ridge G of the roof-type mirror 3 and 2
Since the light is distributed to the two line sensors 4A and 4B, the image of the pixel in the vicinity of the optical axis AX has a small amount of light for image formation. For this reason, the brightness of the image on each of the line sensors 4A and 4B (a white paper surface having a uniform reflectance is used as the original image, and the line sensor is illuminated by the imaging lens 1 in the main scanning direction as described above. The light intensity distribution on the light receiving element array line in the line sensor when imaged on 4A and 4B, and this light intensity distribution is referred to as the shading shape). The maximum value is normalized to 100% as shown in FIG. Represented by. In FIG. 7, the 0 point on the horizontal axis indicates the position of the light receiving element corresponding to the optical axis of the imaging lens in the line sensor.

As is apparent from FIG. 7, the brightness of the image is extremely small in the light receiving element portion corresponding to the pixels in the vicinity of the optical axis, so that the output signals from these light receiving elements have a small S / N ratio. It is difficult to optimize the signal even with the above-mentioned shading correction, and when the original image is reproduced with the combined read signal, the line sensors 4A and 4B
Therefore, the seam of the read image becomes conspicuous due to the decrease in the S / N ratio.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and in the document reading apparatus of the document reading system as described above, the seam portion of the divided image read by each line sensor. It is an object of the present invention to provide a novel document illuminating device that can effectively reduce the decrease in the S / N ratio of a signal in the case of.

[0013]

According to the document illuminating device of the present invention, "a document to be read is illuminated in a slit shape elongated in the main scanning direction, and an image of an illuminated portion by the imaging lens is imaged by a roof mirror. Is divided into two parts in the main scanning direction with respect to the optical axis of, and the divided images are formed on separate line sensors, and the output of each line sensor is combined into a signal in the main scanning direction. A device for illuminating an illuminating unit, which includes a tubular lamp, a reflecting means, and a light shielding means.

The "tubular lamp" is arranged parallel to the main scanning direction. As the tubular lamp, a halogen lamp or a fluorescent tube lamp exemplified in the examples described later can be used. As described above, the "main scanning direction" refers to a direction corresponding to the light receiving element array direction of the line sensor in the reading illumination unit when the line sensor and the reading illumination unit are connected in an image forming relationship with each other by the imaging lens. In the reading illumination unit, the direction orthogonal to the main scanning direction is the sub scanning direction. It should be noted that the line sensor is R for reading a color image.
It includes a system for reading a plurality of lines, such as a system in which light receiving elements provided with color separation filters of (red), G (green), and B (blue) are arranged in three lines. In such a case, it is needless to say that the illuminance in the sub-scanning direction in the reading illumination unit needs to be sufficiently large for a plurality of lines to be read.

The "reflecting means" is provided along the longitudinal direction of the tubular lamp, and collects the light from the tubular lamp on the reading illumination unit in the form of a slit elongated in the main scanning direction. As this reflecting means, a "concave reflecting mirror that surrounds the tubular lamp halfway in the longitudinal direction" can be used. Furthermore, along with this concave reflecting mirror, "a concave lamp reflecting the tubular lamp along the side opposite to the concave reflecting mirror through the tubular lamp" It is possible to use an "opposite reflector provided" (claim 6).

The "light-shielding means" shields the reading illumination unit from direct light from the tubular lamp.

According to another aspect of the document reading apparatus of the present invention, "a light-shielding unit has an opening formed at a central portion in a direction corresponding to the main scanning, so that a vicinity of an intersection between the reading illumination unit and the optical axis of the imaging lens is formed.
The shape and size of the opening of the light shielding unit are adjusted so that the original reading unit illuminates with the light reflected by the reflecting unit and the direct light from the tubular lamp. " .. The optical axis of the imaging lens is bent along with the optical path when the optical path is bent by a reflecting member provided in the imaging optical system or the like.

According to another aspect of the document reading apparatus of the present invention, "the opening is formed in the central portion of the light shielding means in the main scanning corresponding direction, so that the vicinity of the intersection of the reading illumination section and the optical axis of the imaging lens is formed.
The shape and size of the opening in the light shielding unit are adjusted so that the document reading unit is illuminated by the light reflected by the reflecting unit and the direct light from the tubular lamp, and the shape and size of the light shielding unit are adjusted. The effective reflection width is increased in the central portion in the main scanning corresponding direction. " Here, the effective reflection width in the reflection means,
It is the width of the reflection surface that effectively contributes to the illumination of the reading illumination unit in a cross section obtained by virtually cutting the reflection unit with a plane orthogonal to the longitudinal direction of the tubular lamp.

The "opening" in the light shielding means may be formed as a "cutout" (claim 3), or the light shielding means may be "paired with a supporting substrate whose longitudinal direction corresponds to the main scanning direction". The pair of eaves plates may be arranged side by side in the longitudinal direction of the supporting substrate with a space therebetween and screwed to the supporting substrate, and the openings may be formed by the intervals of the eaves plates. In this case, it is possible to adjust the position and width of the opening by making the screw fixing portion a long hole that is long in the longitudinal direction of the support substrate (claim 4).

It is also possible to provide adjusting means for adjusting the displacement of the light shielding means in the main scanning corresponding direction (claim 6). Further, when the reflecting means is composed of the concave reflecting mirror and the counter reflecting plate as described above, the effective reflection width of the counter reflecting plate can be increased in the central portion corresponding to the main scanning direction (claim 7).

The illuminated original may be reflective or light-transmissive, and the original is illuminated from the image side in the former case and from the rear side in the latter.

[0022]

As described above, according to the present invention, the central portion of the reading illumination unit (in the vicinity of the intersection with the optical axis of the imaging lens) is illuminated by not only the light flux reflected by the reflecting means but also the direct light from the tubular lamp. Therefore, the “shading shape” forms a mountain shape in the central portion. This "mountain of illuminance distribution"
Thus, the shading distribution on the line sensor is flattened.

[0023]

EXAMPLES Specific examples will be described below.

In FIG. 1A, reference numeral 10 indicates a contact glass. Document 0 with image to be read
Is placed flat on the contact glass 10 with the image surface facing the contact glass 10. The tubular lamp indicated by reference numeral 12 is a halogen lamp, and its longitudinal direction is shown in FIG.
It is arranged in a direction orthogonal to the drawing of (A). A concave reflecting mirror 14 and a counter reflecting plate 16 which constitute a reflecting means are arranged along the tubular lamp 12.

The concave reflecting mirror 14 is provided so as to surround the tubular lamp 12 halfway in the longitudinal direction thereof, and the counter reflecting plate 16 is provided with the concave reflecting mirror 14 via the tubular lamp 12.
It is provided along the tubular lamp 12 on the opposite side.

The mirror surface of the concave reflecting mirror 14 is a tubular lamp 12.
So that a part of the light from the light is focused and reflected toward the contact glass side, and the other part of the light is reflected by the counter reflection plate 1.
It is defined to reflect the light in a focused manner toward the position 6. Therefore, when the tubular lamp 12 is caused to emit light, a part of the light is focused and reflected by the concave reflecting mirror 14, and the contact Dallas 1
On the document mounting surface of 0, light is condensed into an extremely thin slit having a longitudinal direction in the direction orthogonal to the drawing (this condensing unit is a reading illumination unit).

The counter reflecting plate 16 is a plane mirror in this embodiment and does not have a function of converging a light beam by itself, but it is focused by the concave reflecting mirror 14 and reflects incident light to read the light. Irradiate the illumination unit in a focused manner. The counter reflecting plate 16 also reflects the direct light from the tubular lamp 12 toward the document placement surface side, but this direct light is divergent and does not have a function of converging the light flux on the counter reflecting plate itself, so that it is read. It does not substantially contribute to the illumination of the illumination unit.

In order to effectively contribute the light which is directly incident on the counter reflecting plate 16 from the tubular lamp 12 to the illumination of the reading illumination section, it is possible to use a cylindrical concave mirror for the counter reflecting plate. On the contrary, when sufficient illumination illuminance can be obtained only by the concave reflecting mirror 14, the counter reflecting plate 16 can be omitted.

Reflected light from the reading illumination unit (shown by a broken line. This broken line represents an optical axis ray of an imaging lens (not shown),
Therefore, the optical axis of the image forming lens is coincident with the optical axis of the image forming lens, and is reflected by the mirror 20 and guided onto a pair of line sensors through the image forming lens and a roof mirror (not shown), and the optical axis of the image forming lens is changed. A divided image, which is divided into two in the main scanning direction as a boundary, is formed on each line sensor. Each time one of the line sensors is driven, one line or a plurality of lines of the document 0 are main-scanned. In order to perform the sub-scan, for example, in the state shown in FIG. 1A, the original 0 together with the contact glass 10 may be moved to the left in the figure at a predetermined speed. As the method of sub-scanning the read document, various methods are conventionally known in addition to the above method, and these known sub-scanning methods can be appropriately used.

The light-shielding means indicated by reference numeral 18 is a concave reflecting mirror 1.
4 is provided between the contact glass 10 and the contact glass 10 to block direct light from the tubular lamp 10 from the reading illumination unit.

As shown in FIG. 1B, the opening 1 formed by a rectangular cutout is formed in the central portion of the light shielding means 18 in the main scanning direction.
8A is formed. Therefore, the central portion in the main scanning direction of the reading illumination unit is illuminated by the direct light from the tubular lamp 12 as well as the light reflected by the reflecting means. Therefore, the shading shape in the reading illumination unit has a peak of the illuminance distribution in the central portion in the main scanning direction, and the shortage of the amount of light received by the light receiving elements near the optical axis of the imaging lens of each line sensor is resolved.

FIG. 1C shows a modification, which is a light shielding means 1
The opening 18 formed in 8 has a triangular shape. The apex of the triangular cutout corresponds to the intersection of the optical axis of the imaging lens and the reading illumination unit. Such a triangular opening has the effect of narrowing the “peak width” of the illuminance distribution peaks formed in the central portion of the reading illumination unit (intuitively, the shape of the illuminance distribution peaks approaches a delta function). Therefore, it is effective when the shading distribution described with reference to FIG. 7 changes sharply near the origin of the horizontal axis.

The peaks of the illuminance distribution formed in the central portion of the reading illumination unit in the main scanning direction corresponding to the openings 18A and 18B have the "top" positions at the intersections with the optical axis of the imaging lens. It is ideal to do. This matching is easy in terms of the design of the document illuminating device, but it is difficult to realize the above matching without any adjustment work in consideration of an assembling error when actually assembling the document illuminating device to the document reading device.

Therefore, in the embodiment shown in FIG.
The shading means 18 having A and 18B (FIGS. 2A and 2B) is displaceable in the longitudinal direction (direction corresponding to main scanning), and a drive rod having a worm wheel 20 is provided at the longitudinal end of the shading means 18. By rotating the worm wheel 21 meshed with the worm wheel 20 by the rotation of an adjusting knob (not shown) connected to the worm wheel 21, it is possible to adjust the displacement of the light shielding means 18 in the main scanning corresponding direction. The peaks of the illuminance distribution can be easily aligned with the intersections of the reading ridges and the optical axis of the imaging lens.

The embodiment shown in FIG. 3 is an embodiment of the original illuminating device according to claims 4 and 5. The light shielding unit 180 includes a support substrate 181 whose longitudinal direction corresponds to the main scanning direction and a pair of eaves plates 18.
2, 183. A pair of eaves plates 182,1
83 are arranged in the longitudinal direction of the support substrate 181 with a space between each other, and are screwed on the support substrate 181.
It is screwed by 3,194. The screw stoppers are long holes 182A, 182 that are long in the longitudinal direction of the support substrate 181.
By setting B, 183A, and 183B, the eaves board 18
The position and width of the opening can be adjusted by the interval of 2,183. Since the peak width of the illuminance distribution can be changed by adjusting the width of the opening, a peak having an appropriate illuminance distribution can be formed according to the shading distribution.

In the embodiment of FIG. 3, the displacement of the entire light shielding means 180 can be adjusted in the main scanning corresponding direction in the same manner as the embodiment of FIG. The drive rod having the worm wheels 20 and 21 shown in FIGS. 2 and 3 and an adjusting knob (not shown) constitute an adjusting means.

In the embodiment described with reference to FIGS. 1 to 3,
The manuscript was a reflection type manuscript and was placed on the contact glass and illuminated through the contact glass. On the other hand, in the embodiment shown in FIG. 4, the original document OR is light transmissive like a microfilm, and as shown in FIG.
While being held by the holder 25, it is illuminated from the back side of the document through the diffusion plate 27.

Reference numeral 14A indicates a concave reflecting mirror, and reference numeral 16A indicates a counter reflecting plate. The light transmitted through the original document OR is reflected by the mirror 20, and is formed as a divided image on a pair of line sensors by an image forming system including an image forming lens and a roof mirror. As shown in FIG. 4B, the light shielding unit 190 has an opening formed by a notch at the center in the longitudinal direction corresponding to the main scanning direction. Since the diffusion plate 27 has the function of “leveling” the peaks of the illuminance distribution formed by the openings, it is preferable to place it as close to the holder 25 as possible in order to minimize this leveling.

The light shielding means can be configured as shown in FIG. 1 (C) or FIGS. 2 and 3 even in the document illuminating device of FIG.

In the embodiment described above, the shading distribution in each light receiving portion of the pair of line sensors is flattened only by the opening in the light shielding means. However, if the shape in the vicinity of the origin in the shading distribution (see FIG. 7) becomes too steep, it becomes difficult to effectively flatten the shading distribution only in the opening.

Referring now to FIG. 6, this figure shows the illuminance distribution in the vicinity of the central portion of the reading illumination unit in the main scanning direction. The direction of the horizontal axis is the main scanning direction, and the intersection of the vertical and horizontal axes is the intersection of the reading illumination unit and the optical axis of the imaging lens. Figure 6
(A) and (B), a mountain-shaped curve 6-1 indicated by a solid line
Shows an "ideal shape of peaks of the illuminance distribution to be formed by the openings of the light shielding means in order to effectively flatten the shading distribution on the line sensor". In such a case, when the width of the opening is increased in order to obtain the peak illuminance in the curve 6-1, the peaks of the illuminance distribution actually formed have the peak width 6- as shown by the curve 6-2. It becomes larger than 1, and it is difficult to flatten the shading distribution well. Conversely, when the width of the opening is set to be narrow, the peak width of the peak of the actual illuminance distribution becomes substantially equal to the width of the ideal curve 6-1 as shown by the curve 6-3 in FIG. 6B. The height of the crest is lower than that of the curve 6-1 and the illuminance becomes insufficient, so that the shading distribution cannot be effectively flattened.

In such a case, the shape and size of the opening in the light-shielding means are adjusted so that a desired shading shape is realized in the document reading section, and the effective reflection width in the reflecting means is set in the main scanning corresponding direction. It should be large in the center.

FIG. 5 shows an example in which the effective reflection width of the counter reflection plate constituting the reflection means is increased in the central portion corresponding to the main scanning direction.
It is illustrated. The counter reflection plate 16B shown in FIG.
Although it is the same as that described with reference to FIG. 1, the hatched portion of the reflection surface portion is masked so that it does not reflect light. The width indicated by reference numeral D is an effective reflection width in the counter reflection plate 16B, and is set to be "large in the central portion corresponding to the main scanning direction" as is clear from the drawing. Therefore, the amount of light focused on the reading illumination unit by the counter reflecting plate 16C is suppressed in other portions than in the central portion in the main scanning corresponding direction.

In this case, the peak of the illuminance distribution due to the direct light from the tubular lamp passing through the opening of the light shielding plate is as shown by the curve 5-1 in FIG. 5C, and the effective reflection width D of the counter reflection plate 16C is shown.
The peak of the illuminance distribution due to the change of is like the curve 5-2 in the figure. When these are combined in the reading illumination unit, the peak of the illuminance distribution like the curve 5-3 near the reading illumination unit is steep. Can be formed. A curve 5-4 in FIG. 5D is a peak of the illuminance distribution necessary for flattening the shading distribution on the line sensor, and the illuminance distribution close to ideal is realized by the opening and the change in the effective reflection width. To be done.

In order to change the effective reflection width as described above,
Instead of masking the reflective surface as shown in FIG.
The shape of the reflection surface itself may be changed as in the case of the counter reflection plate 16C shown in FIG.

[0046]

As described above, according to the present invention, it is possible to provide a novel document illuminating device in a document reading device. Since the document illumination device of the present invention is configured as described above,
When one line of a document is distributed to a pair of line sensors and is read with high resolution, it is possible to effectively prevent a decrease in the S / N ratio at the joint portion of the divided images read by each line sensor.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating another embodiment.

FIG. 3 is a diagram for explaining another embodiment.

FIG. 4 is a diagram for explaining still another embodiment.

FIG. 5 is a diagram for explaining an embodiment of the invention of claim 2;

FIG. 6 is a diagram for explaining the invention of claim 2;

FIG. 7 is a diagram for explaining a problem to be solved by the invention.

FIG. 8 is a diagram illustrating document reading by a document reading device to which the present invention is applied.

[Explanation of symbols]

0 Document 10 Contact Glass 12 Tubular Lamp 14 Concave Reflector 16 Opposing Reflector 18 Shading Means 18A Opening

Claims (7)

[Claims] 1. An original to be read is illuminated in a slit shape elongated in the main scanning direction, and an image of an illuminated portion by an imaging lens is detected by a roof mirror in the main scanning direction with an optical axis of the imaging lens as a boundary. In a document reading device that divides and forms divided images on separate line sensors and combines the output of each line sensor into a signal in the main scanning direction, a tubular lamp arranged parallel to the main scanning direction. A reflecting means which is provided along the longitudinal direction of the tubular lamp and focuses the light from the tubular lamp on the reading illumination section in the form of a slit long in the main scanning direction; A light blocking means for blocking the direct light from the lamp, and by forming an opening at the center of the light blocking means in the main scanning corresponding direction, near the intersection of the reading illumination section and the imaging lens optical axis. To The shape and size of the opening in the light shielding unit are adjusted so that the light reflected by the reflecting unit and the direct light from the tubular lamp are illuminated and the desired shading shape is realized in the document reading unit. A document illuminating device characterized by the above. 2. A document to be read is illuminated in a slit shape elongated in the main scanning direction, and an image of an illuminated portion by an imaging lens is detected by a roof mirror in the main scanning direction with the optical axis of the imaging lens as a boundary. In a document reading device that divides and forms divided images on separate line sensors and combines the output of each line sensor into a signal in the main scanning direction, a tubular lamp arranged parallel to the main scanning direction. A reflecting means which is provided along the longitudinal direction of the tubular lamp and focuses the light from the tubular lamp on the reading illumination section in the form of a slit long in the main scanning direction; A light blocking means for blocking the direct light from the lamp, and by forming an opening at the center of the light blocking means in the main scanning corresponding direction, near the intersection of the reading illumination section and the imaging lens optical axis. To Illuminating with the reflected light from the reflecting means and the direct light from the tubular lamp, and adjusting the shape and size of the opening in the light shielding means so as to realize a desired shading shape in the document reading section, Further, the document illuminating device is characterized in that the effective reflection width of the reflecting means is increased at the central portion in the main scanning corresponding direction. 3. The original illuminating device according to claim 1 or 2, wherein the opening in the light shielding means is formed by a notch. 4. The original illuminating device according to claim 1 or 2, wherein the light-shielding means comprises a support substrate whose longitudinal direction corresponds to the main scanning direction and a pair of eaves plates, and the pair of eaves plates. Is arranged in the longitudinal direction of the supporting substrate with a space and is screwed to the supporting substrate, and the screwing portion is a long hole long in the longitudinal direction of the supporting substrate. A document illuminating device characterized in that it is adjustable. 5. The document illuminating device according to claim 1, 2 or 3 or 4, further comprising adjusting means for adjusting the displacement of the light shielding means in the main scanning corresponding direction. 6. The document illuminating device according to claim 1, 2 or 3 or 4 or 5, wherein the reflecting means includes a concave reflecting mirror that surrounds the tubular lamp halfway in the longitudinal direction, and the concave reflecting mirror through the tubular lamp. An original illuminating device having a counter reflecting plate provided along the tubular lamp on the opposite side. 7. The document illuminating device according to claim 2, wherein the reflecting means includes a concave reflecting mirror that surrounds the tubular lamp halfway in the longitudinal direction, and a tubular lamp on the side opposite to the concave reflecting mirror through the tubular lamp. A document illuminating device, comprising: a counter reflecting plate provided along the counter reflecting plate, wherein an effective reflection width of the counter reflecting plate is increased in a central portion corresponding to a main scanning direction.