JPH03129965A - Illuminator for picture reader - Google Patents

Abstract

PURPOSE:To prevent the dispersion in the color reproduction and uneven density of an output picture by adopting the constitution such that the illuminating light quantity distribution in the scanning direction is made substantially flat in a range of 7mm or over. CONSTITUTION:The illuminating light quantity distribution of a illuminator 5 on an original in the scanning direction is made substantially flat in a range of 7mm or over especially. Thus, dispersion in the color reproducibility, the density unevenness of an output picture due to the magnification of the picture element array interval of a 3-line color sensor 3 on the original, the magnification of the area in the scanning direction read simultaneously and a change in a read position of the color sensor 3 caused by the position of the scanning mechanism resulting from a mount angle error of an optical lens 9 and scanning mirrors 6-8 are prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reading device for manually reading image data such as a digital copying machine, facsimile machine, printer, etc.
The present invention relates to an illumination device for an image reading device that reduces an illuminated optical image of a color document using a scanning mirror system and an optical lens and sequentially forms the image on a reading sensor.

[Prior Art] For example, in a copying machine, an image reading device with a reduction optical system is used. A mirror unit consisting of a fluorescent lamp or halogen lamp that illuminates the original to be formed, a full rate mirror (FRM) and a half rate mirror (HRM) that scan and transmit the optical image, and the image sent from this mirror unit. It is composed of optical lenses and the like that reduce the optical image and form it on the organic photosensitive material belt.

On the other hand, digital color copying machines have been developed and researched in recent years, and the present applicant has previously filed an application regarding this digital color copying machine (for example, Japanese Patent Application Laid-Open No. 63-292195
No. etc. This digital color copying machine converts color original images into the three primary colors of light: red (R), edge (G), and blue (B).
An imaging input terminal (IIT) is provided for reading each image and converting the read data consisting of a light intensity signal into an electric digital density signal by photoelectric conversion.

This IIT is equipped with an exposure lamp, a rod lens array for reading original images, and a CCD line sensor.
An imaging unit that scans a document and optically reads the image; a drive unit that moves the imaging unit; and an electric unit that performs conversion processing on the electrical read signal photoelectrically converted by the CCD line sensor. It consists of various hardware, etc.

According to such a digital color copying machine, since image signals are digitally processed, various types of processing can be easily performed, and high-quality color copies can be made.

[Problem to be solved by the invention]

Incidentally, since the 11T imaging unit in such a digital copying machine is a contact type image reading device, its structure is relatively large. Also,
In the case of a close-contact type, the depth of focus of the reading optical system is shallow, and if the document is lifted off the platen glass, the scanned image will be stuck in the pocket and cannot be read, making it difficult to place the document on the document table. . Furthermore, for copying machines that can copy originals up to 43 editions, which are most commonly used, a CCD sensor with a length longer than the short side of A3 paper (297 mm) is required, but in reality, multiple CCD sensors are required. They are arranged in a staggered manner to form something equivalent to this length. However, in this case, the signal processing becomes complicated, and not only a CCD sensor but also a large number of signal processing boards (A/D converter, image processing system) are required, which increases cost.

Therefore, it is conceivable to apply the aforementioned reduction type image reading device to the IIT of such a digital color copying machine. In this way, any of the problems of the close-contact type described above can be solved.

By the way, as a reading sensor consisting of a CCD line sensor, a 3-line color sensor (3-color line sequential sensor) has been developed in which three pixel rows are arranged above and below using color filters having each of R, G, and B spectral sensitivities. ing. When this color sensor is applied to the IIT of the digital color copying machine described above, the pixel rows of the 3-line color sensor are
Since they are arranged with a gap in the J scanning direction, if the illumination of the document is sharply distributed in the sub-scanning direction, B and G.

The color balance of the CCD output for each R color increases, resulting in problems such as poor color reproducibility and a high rate of defective products of manufactured IIT. Also, in the case of reduced type,
If there are variations in the installation angles of the optical lenses and reflecting mirrors in the scanning system, the reading position in the sub-scanning direction will change. Similarly, if the illumination of the document is sharply distributed in the sub-scanning direction, the reading position in the sub-scanning direction will change. This causes a problem in that the output of the sensor fluctuates within the image, resulting in uneven density in the output image.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems so that color reproducibility for a reading device such as a digital color copying machine using a 3-line color sensor is well reproduced without variation, and density unevenness is prevented in an output image. An object of the present invention is to provide a lighting device that does not cause

[Means to solve the problem]

The illumination device of the image reading device of the present invention scans a slit-shaped area of a document in a direction crossing it using a plurality of relatively movable scanning mirrors, reduces the scanned image using an optical lens, and displays the scanned image on a three-line color sensor. An illumination device for an image reading device that reads a color document image by forming an image on the image, the illumination device having an illumination light amount distribution in the scanning direction of at least 7 mm.
It is configured to be substantially flat within the above range.

For this purpose, the illumination device is composed of a lamp and a flat reflector facing the lamp, and the distribution of light that directly illuminates the document from the lamp and the distribution of light reflected from the flat reflector facing the lamp on the document are different. By overlapping them, instead of lowering the intensity of the illumination light in the central part, the light quantity distribution in the peripheral part can be improved and the light quantity distribution in the scanning direction can be flattened. Alternatively, the lighting device may be constructed of a lamp and a folded plane mirror that is bent in the middle of facing the lamp so as to form an angle with each other. In this case, the folded plane mirror can be made into a Fresnel mirror. Furthermore, it is desirable to be able to adjust the angle and position of these reflecting mirrors with respect to the lamp.

In addition, the illumination device is constructed by arranging two aperture-type lamps symmetrically across the optical axis, so that the distribution of light illuminating the document from one lamp and the distribution of light illuminating the document from the other lamp are different. The light intensity distribution in the scanning direction may be flattened by overlapping the light beams to improve the light intensity distribution in the peripheral portion thereof.

In that case, it is desirable to configure the aperture type lamp so that its angle can be adjusted around its axis.

[Effect]

The pixel row spacing of the 3-line color sensor has been expanded on the original to 3-4 mm or more, and due to angular errors in the mounting of the optical lens and scanning mirror, the reading position of the 3-line color sensor changes depending on the position of the scanning mechanism. However, by configuring the illumination device so that the illumination light amount distribution in the scanning direction is substantially flat in a range of at least 7 mm or more, color reproducibility deteriorates due to the above reasons, and
No density unevenness occurs in the output image.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1(a) is a diagram showing a schematic configuration of a reduced-sized image input terminal (IIT) 1 of a color copying machine to which the illumination device of the present invention is applied. This FITl is composed of a platen glass 2, an optical scanning mechanism, and a 3-line color sensor 3 for reading.

The optical scanning mechanism includes an illumination device 5 according to the present invention for illuminating the document on the platen glass 2 (details will be described later);
1 Full Rate Mirror
ror; FRM) 6 and a pair of half-rate mirrors ()lf Rate Mirror; HRM)
? , 8, and an optical lens 9 that forms an image on the reading sensor 3. F.R.M.
6 is inclined at approximately 45° with respect to the platen glass 2, and is attached to the first carriage 10 with its reflective surface facing upward to the left in the figure. Similarly, the lighting device 5 is also mounted on the first carriage 10.

The first carriage 10 is movable in the sub-scanning direction of the color copying machine (rightward in the figure). This allows scanning for reading the original on the platen glass 2.

Further, a pair of HRMs 7.8 are provided in the second carriage 11 so as to be inclined by approximately 45 inches with respect to the platen glass 2 and to be vertically overlapped.

In that case, the upper HRM? The reflective surface of the lower HRM 8 faces toward the lower right in the figure, and the reflective surface of the lower HRM 8 faces toward the upper right in the figure. By arranging the mirrors 6, 7, and 8 in this manner, an optically read image of the document on the platen glass 2 is introduced into the optical lens 9.

The second carriage 11 is also movable in the sub-scanning direction. Then, the moving speed v1 of the first carriage lo is the second
The moving speed v2 of the carriage 11 is set to be twice as large. In this way, the first and second caliber 1
By setting the speed ratio of 0.11 to 2, the moving distance of FRM6 is always twice the moving distance of HRM7.8. Therefore, no matter what position each mirror 6.7.8 moves to, the optical path length from the original to the optical lens 9 is always constant (for example, 500 mm in the example of FIG. 1(b)) (i.e., the original (The distance from the image at any position to the optical lens 9 is constant.) Therefore, the light from the illumination device 5 illuminates the original on the platen glass 2, and the reflected light from the original is reflected at the FRM 6 and HRM 7.8. After being reflected, the optical lens 9 forms an image on the three-line color sensor 3 at a constant magnification.

To obtain a full color copy, FRM6 and HRM
7.8 requires repeating four scans (for each of black, red, green, and blue).

By the way, as shown in FIG. 1(d), the CCD reading sensor 3 has pixels that are sensitive to each color by color filters having spectral sensitivities of red (R), green (G), and blue (B). It is defined as a 3-line color sensor (3-color line sequential sensor) 12 in which columns 12a, 12b, and 12c are arranged one above the other. Currently, the pixel row interval of this 3-line color sensor 12 is 168 μm, and if the reduction ratio is 1/10, the distance in the scanning direction of the optical scanning mechanism on the document is 1.68 μm.
Corresponds to mm. As shown in FIG. 1(e), row R and row B
The gap between the corresponding positions of the rows is twice that, 3.36 mm. Therefore, at least 3
．． If the illumination by the illumination device 5 is not uniform in a range of 36 mm or more, the color balance between the three colors will be disrupted, resulting in poor color reproducibility. In addition, if there is an angular error in the installation of the optical lens 9 and each mirror 6, 7, 8, the position read by the reading sensor 3 will change depending on the position of the scanning mechanism (the optical axis in Fig. 1 is aligned with the original). This means that the intersecting position changes relative to the illumination device W15). Therefore, the output of the sensor fluctuates, causing density unevenness in the output image. This is a problem specific to a reduced-sized scanning reader, but it becomes a big problem when combined with the problem caused by the above-mentioned three-line color sensor 12 having a wide reading position in the sub-scanning direction.

Accordingly, in the present invention, the illumination light amount distribution of the illumination device 5 on the document in the sub-scanning direction is made substantially flat at least within a predetermined distance range, particularly within a range of 7 rnm or more. Here, "substantially flat" means that the variation in light amount is within 10%. As long as the above numerical range is satisfied, as a rule of thumb, color reproducibility will deteriorate.
Moreover, density unevenness does not occur in the output image. If the flattening range is smaller than this range, color shift and density unevenness will occur in the reproduced image in a reduction type image reading device such as the present invention.

In order to satisfy such requirements, in the present invention,
A lighting device as shown in FIGS. 2(a) to 2(a) is employed. First, in the case of (a) in the figure, a plane mirror 14 is used as a reflecting mirror disposed opposite a fluorescent lamp or a halogen lamp 13 in order to increase illumination efficiency. Next, the one shown in Fig. b) uses a folded plane mirror 15 which is arranged to face a fluorescent lamp or a halogen lamp 13 and is bent in the middle so that they form an angle with each other. The one shown in (C) of the figure is a 7-Renel mirror 15' of the one shown in (B) of the figure. In the case shown in (d) of the figure, two aperture type fluorescent lamps or halogen lamps (aperture lamps) are arranged symmetrically so as to sandwich the optical axis 13', 13'. From (a) to (
In C), in order to eliminate the steep distribution of illumination light, there is a distribution of light that directly illuminates the document from the lamp 13 and a distribution of light that is reflected from the reflector 14, 15 or 15' facing the lamp, on the document. Instead of reducing the intensity of the illumination light in the central area, the light intensity distribution in the peripheral area is improved, and as a result, the light intensity distribution in the sub-scanning direction is flattened within the range mentioned above. It is something that exists. Furthermore, the reflecting mirror 14.
It is more desirable if the angle and position of the lamp 15 and 15' with respect to the lamp 13 can be adjusted to flatten the light intensity distribution. In addition, in the case of (a) in the figure, in order to similarly eliminate the steep distribution of illumination light, the distribution of light illuminating the original from lamp 13' and the distribution of light illuminating the original from lamp 13' are overlapped. In addition, the light amount distribution in the peripheral portion is improved, and as a result, the light amount distribution in the sub-scanning direction is flattened within the above-mentioned range. In addition, in the case of (d) in the figure, it is better to make the angle of the aperture lamps 13' and 13' adjustable as shown by the arrows in the figure, so that the light intensity distribution in the sub-scanning direction can be adjusted evenly. desirable.

Furthermore, instead of the two lamps 13', 13', it is also possible to configure them with one U-shaped halogen lamp. If you do this, one end (bottom side of the U-shape)
Since there is no need to provide electrodes in the display, space can be saved and variations in the distance between the two light emitting parts can be reduced.

FIG. 3 shows a light amount distribution diagram in the sub-scanning direction to show that, for example, the method shown in FIG. 2(a) is effective in flattening the light amount distribution. Curve A has a radius of 7.75 mm for the lamp 13;
Aperture angle 50°, lamp 1 from platen 2 surface
3, the distance to the center is 16 mm, 1 the distance from the center of the lamp 13 to the lower end of the plane mirror 14 is 13.98 mm, and the light intensity distribution is shown when the plane mirror 14 is tilted at 60 degrees from the horizontal plane. It shows the light amount distribution when the plane mirror 14 is tilted at 50° from the horizontal plane. The ranges of 90% of the peak values of these light amount distributions are 8.3 mm and 7.8 mm, respectively, which are within the numerical ranges described above. On the other hand, curve C shows the light intensity distribution of a conventional model using a spherical mirror with a radius of 14 mm instead of the plane mirror 14 (the other conditions are the same), and the range of 90% of the peak value is 4°5 mmL. Rather, such an illumination device can be satisfactorily used as an illumination device for an image reading device such as the present invention, which reduces a scanned image using an optical lens and forms the image on a three-line color sensor to read a color document image. It is clear that it cannot be done.

〔Effect of the invention〕

As described above, in the present invention, a slit-shaped area of a document is scanned by a plurality of relatively movable scanning mirrors in a direction crossing the slit-shaped area of the document, and the scanned image is reduced by an optical lens and displayed on a three-line color sensor. In an illumination device for an image reading device that forms an image and reads a color original image, the illumination device is configured so that the illumination light amount distribution in the scanning direction is substantially flat in a range of at least 7 mm or more. The pixel row interval of the line color sensor is expanded on the document, and the area to be read simultaneously in the scanning direction is expanded. Also, due to angular errors in the mounting of the optical lens and scanning mirror, the reading of the 3-line color sensor depends on the position of the scanning mechanism. Deterioration in color reproducibility and density unevenness in output images caused by changes in position do not occur.

[Brief explanation of the drawing]

FIG. 1(a) is a schematic configuration diagram of a reduced-sized image input terminal of a color copying machine to which the illumination device of the present invention is applied, and FIG. 1(b) and (C) are a plan view and side view showing its optical development. 1(a) is a front view of a 3-line color sensor, FIGS. 2(a) to 2(a) are side views of an embodiment of the illumination device of the image reading device of the present invention, and FIG. 3 is a sub-scanning It is a figure which shows the example of the light quantity distribution of a direction. 1: Reduced image input terminal (IIT),
2 Nibraten glass, 3: 3-line color sensor for reading, 4: Mirror unit, 5: Illumination device, 6: Full Rate Mirror (FRM)
), 7.8: Half rate mirror () lf Ra
te Mirror; HRM), 9: Optical lens, 10: First carriage, 11: Second carriage, 12
:3 line color sensor (3 color line sequential sensor), 12a
s 12b-12c: pixel row, 13: fluorescent lamp or halogen lamp, 13', 13': aperture type fluorescent lamp or halogen lamp (anoku-char lamp>, 14: plane mirror, 15: plane mirror bent in the middle) Folded plane mirrors at an angle to each other, 15': Fresnel mirror

Claims (8)

[Claims] (1) A plurality of relatively movable scanning mirrors scan a slit-shaped area of the document in a direction intersecting the slit-shaped area, and the scanned image is reduced by an optical lens and formed on a 3-line color sensor to form a color document image. An illumination device for an image reading device for reading an image, characterized in that the illumination device is configured so that the illumination light amount distribution in the scanning direction is substantially flat over a range of at least 7 mm or more. Device. (2) The illumination device is composed of a lamp and a flat reflector facing the lamp, and the distribution of light that directly illuminates the document from the lamp is overlapped with the distribution of light reflected from the flat reflector facing the lamp on the document. In addition, the image reading device according to claim 1, characterized in that instead of lowering the intensity of the illumination light in the central portion, the light amount distribution in the peripheral portion is improved to flatten the light amount distribution in the scanning direction. lighting equipment. (3) The illumination device consists of a lamp and a folded plane mirror that is bent in the middle to form an angle with each other, and the distribution of light that illuminates the document directly from the lamp and the light that is reflected from the folded plane mirror that faces the lamp. By superimposing the distribution of light on the original document, instead of reducing the intensity of the illumination light in the center, the light intensity distribution in the surrounding area is improved.
2. The illumination device for an image reading device according to claim 1, wherein the light amount distribution in the scanning direction is flattened. (4) The illumination device for an image reading device according to claim 3, wherein the bending plane mirror is a Fresnel mirror. (5) The illumination device for an image reading device according to any one of claims 2 to 4, wherein the position and angle of the plane mirror with respect to the lamp are adjustable. (6) The illumination device consists of two aperture-type lamps arranged symmetrically across the optical axis, and the distribution of light illuminating the document from one lamp and the distribution of light illuminating the document from the other lamp. 2. The illumination device for an image reading device according to claim 1, wherein the illumination device is arranged such that the light amount distribution in the scanning direction is flattened by overlapping the light amount distribution in the scanning direction. (7) The illumination device for an image reading device according to claim 6, characterized in that the two aperture-type lamps are replaced by one U-shaped halogen lamp. (8) The illumination device for an image reading device according to claim 6, wherein the aperture type lamp is configured to be adjustable in angle around its axis.