JPS60153668A - Original reader - Google Patents

Abstract

PURPOSE:To attain reading with fidelity by providing a couple of light shield plats puttig a reading light path between so as to narrower the lighting width of an original thereby decreasing a reflected light from a part other than the reading line. CONSTITUTION:The light shield plates 101, 102 are provided while putting a reading light path 11 between. Moreover, a lighting light from a lighting light source 31 is shut partly by the light shield plate 101 and parts a-g of an original 2 on an original platen 1 are lighted. The lighting light from a lighting light source 32 is shut partly by the light shield plate 102 so as to light parts h-d of the original 2. The width of the parts h-g of the original 2 is much narrowered by the presence of the light shield plates 101, 102. Since the reflected light from the part other than the reading line is decreased, the reading is performed with fidelity.

Description

[Detailed Description of the Invention] <Technical Field of the Invention> The present invention relates to an improvement of a document reading device that breaks down image information on a document into minute parts and reads them as electrical signals.0 <Technical Background of the Invention and its Problems Point> In recent years, in addition to the conventional processing of code information, there has been a demand for processing images as information. In this image processing, the document reading device inputs the image.

Originals can be in the form of sheets or books, and there are various types of originals such as not only binary black and white originals but also those with halftones such as photographs, etc., and there is a document reader that can handle these originals. Development of equipment is actively underway.

Document reading devices generally use C and CD line sensors in which a plurality of light receiving elements are arranged in a line. This Cε
Since the distance between each light receiving element of the D line sensor is very narrow and the sensor length is generally shorter than the reading width of the read document, a reduction optical system is required when projecting an image of the read document onto the CCD line sensor. Hereinafter, this reduction optical system will be simply referred to as an optical system.

This optical system consists of an illumination light source such as a halogen lamp or fluorescent lamp that illuminates the document, a reading lens that reduces and projects the image onto the light receiving element of the document's 1ccD line sensor, and a CCD from the document.
It consists of reflective mirrors and the like to form an optical path to the line sensor.

When reading all the contents of a document, move the document and the CCD line sensor relative to each other in a direction perpendicular to the reading line (the portion projected onto the light receiving element of the CCD line sensor), and scan the document '1ccD. The images must be projected one after another onto the light receiving element of the line sensor.

There are various methods for moving the original and the CCD line sensor relative to each other.For example, there are methods of illuminating the entire original and moving the CCD line sensor, and methods of partially illuminating the original and moving the original. There are methods such as a method in which the document is partially illuminated and the CCD line sensor and the optical system are moved as an integral block, and a method in which the document is partially illuminated and the optical system is moved.

FIG. 3 is a schematic diagram of a conventional document reading device that uses a method of partially illuminating the document and moving an optical system. 8th
In the figure, l is a document table made of a transparent glass plate, and the document 2 placed on this document table 1 with its reading surface facing the document table is partially illuminated by a pair of illumination light sources 31 and 32. illuminated. A part of the illuminated original 2 is CC-coded by the reading lens 7 via the reflecting mirrors 4 and 5°6.
A reduced image is formed on the light receiving element portion of the D line sensor 8, and converted into an electrical signal by the CCD line sensor 8.

When reading starts, the illumination light source 31, 82 and reflection mirror 4 are moved together by a drive device (not shown) in a direction perpendicular to the reading line, that is, in the direction shown by the arrow, while maintaining a constant distance from the original 2. Start. Correspondingly, the reflection mirror 5.6 starts moving in the same direction with a movement amount that is half the movement amount of the illumination light source 81.32 and the reflection mirror 4, and the optical path length from the original 2 to the CCD line sensor 8 't remains constant. It is configured to keep the

Through this operation, all the contents of the original document 2 are successively projected onto the light receiving element of the CCD line sensor 8 and converted into electrical signals. The contents of the document 2 that are successively projected and converted into electrical signals are transferred to the storage device and the output device at a certain timing corresponding to the amount of movement of the illumination light sources 81 and 82 and the reflecting mirror 4.

When the reading of the original 2 is completed in this way, 81.
82 and reflecting mirrors 4, 5, 6Ifi read and sometimes move in the opposite direction and end their operation when they return to the initial position.0 Illumination light source 81.82 produces a reduced image of the original 2 on the light receiving element of the CCD line sensor 8. The original 2 is illuminated so that a . The illuminated area of manuscript 2 is quite wide,
There is a margin for including a portion other than that projected onto the light receiving element of the CCD line sensor 8.

Further, 9 is an illumination light source cover that prevents illumination light from leaking to areas other than the document 2.

FIG. 4 is a schematic diagram of the vicinity of the illumination light source of the conventional document reading device shown in FIG. 3 above.

In FIG. 4, the illumination light source 31 passes the document 2 through the document table It.
The illumination light source 32 illuminates the c-d portion of the original 2 by passing through the entire original platen l. Therefore, the portions c and d of the original 2 are illuminated by both the illumination light sources 81 and 82 and are very bright.

Now, if part e-f of manuscript 2 is pure black information, e
The -f part is not only the direct illumination of the illumination light sources 81 and 82 (
Reflected light from the white part surrounding e-f (arrow r
) is further illuminated by the reflected light from the 0-white area Ff4Ld, the periphery of e-f is thicker and uneven illuminance occurs in the e-f portion. And the peripheral part of e-f
The illuminance is higher than that at the center of -f, and the peripheral area of e-f is read as having a lower density than it actually is.

This reflected light from the white portion is caused by the presence of a thick glass plate in front of the original document 2, that is, the document table l, and is a phenomenon that occurs as long as the document table l exists.

The influence of reflected light from white parts is hardly a problem when reading original 2 as a binary image, but it becomes a problem when you want to express halftones, and the black parts surrounded by white parts are different from the actual ones. It can be read as different gray information,
There is a problem in that the peripheral part of a black part of the same density is erroneously read as gray information.

<Object of the Invention> In view of the above-mentioned points, the present invention provides an original that can be faithfully read by reducing the influence of reflected light from areas other than the reading line, especially the influence of white parts existing around the reading line. An object of the present invention is to provide a reading device, and in order to achieve this object, the document reading device of the present invention includes a pair of illumination light sources for illuminating the document, a pair of illumination light sources for illuminating the document, Reading optical path t-
A pair of light-shielding plates are provided in between, and the width of the overlapped portion of the illumination light generated by the pair of illumination light sources generated on the part of the document to be read is narrowed by the pair of light-shielding plates. .

<Embodiment of the Invention> Hereinafter, an embodiment of the present invention will be described in full detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment in which the present invention is applied to a document reading device using a method of partially illuminating a document and moving an optical system, and is the same as the conventional device shown in FIG. Parts are indicated with the same reference numerals.

In FIG. 1, reference numeral 1 denotes an original table made of a transparent glass plate, 2 an original document, 31 and 32 a pair of illumination light sources, and 4
．． 5 and 6 are reflecting mirrors, 7 is a reading lens, 8I/
``1 CCD line sensor, 9 is illumination light source cover, 101
and 1olj a pair of light shielding plates, 1.1 is a reading optical path, 1
Reference numeral 2 denotes a mirror holder, and the document 2 placed on the document table 1 with its V surface to be read facing the document table is connected to a pair of illumination light sources 3.
Partially illuminated by 1.82. illuminated manuscript 2
A part of the image is formed as a reduced image on the light-receiving element portion of the CCD line sensor 8 by the reading lens 7 through the reflection mirror 4.5.6e, and is converted into an electric signal by the CCD line sensor 8. When reading starts, the illumination light sources 31 and 32 and the reflection mirror 4 are activated by a driving device (not shown).
start moving in a direction perpendicular to the reading failure line, that is, in the direction indicated by the arrow, while maintaining a constant distance from the original 2. Correspondingly, the reflecting mirror 5.6 is connected to the illumination source 8.
1.82 and half the amount of movement of the reflecting mirror 4, the movement in the same direction is started, and the CCD line sensor 8 is moved from the document 2.
It is configured to keep the optical path length constant.

FIG. 2 is a schematic diagram illustrating the structure near the illumination light source of the document reading device of the present invention. illuminates portions a to g of the original 2 placed on the original table l. Similarly, a portion of the illumination light from the illumination light source 32 is blocked by a light shielding plate 102 provided opposite to the illumination light source 32, and illuminates a portion h-d of the document 2 placed on the document table l. Therefore, the portion h-g of the original 2 is illuminated by both the illumination light sources 81 and 82, and the illuminance becomes high. The width h-g of this original 2 is slightly narrower than the width c-b in the conventional device shown in FIG. 4 due to the presence of the light-shielding plates 101 and 102. It is constructed so that the illumination light does not reach the area.

Therefore, reflected light from parts other than the reading line is reduced, and the light shielding plates 101 and 1021d and the reading optical path 11t are
- Since they are installed on both sides, direct light and ambient light from the illumination light sources 81 and 32 are prevented from entering the CCD line sensor 8.

Note that 9 is an illumination light source cover that prevents illumination light from leaking to areas other than the original 2. 0 With this configuration, the illumination width of the document by the pair of illumination light sources becomes extremely narrow, the illumination light to areas other than the reading line is reduced, and the illumination light from areas other than the reading line by the glass plate of the document table is reduced. In addition, there is always a high-illuminance area directly above the tip of the light-shielding plate where the illumination light overlaps, and the space between the light-shielding plates forms the reading optical path. Therefore, the high-illuminance portion where the illumination light overlaps always coincides with the reading sill line.

<Effects of the Invention> As described above, according to the present invention, the illumination width of the document by the illumination light source can be narrowed with a very simple structure.
As a result, the illumination light to areas other than the reading line is reduced, and the influence of reflected light from areas other than the reading line due to the presence of the glass plate of the document table, especially the influence of the white area around the reading line. can be reduced. In other words, according to the present invention, even if there is a white part around the scanning line of the original, the density of the entire black area does not decrease, and the density of the black part does not decrease, and the faithful image can be read. Can be read. Therefore, it is very effective for reading not only binary documents but also documents having halftones.

Furthermore, according to the present invention, there is always a high-illuminance area directly above the tip of the light-shielding plate where the illumination light overlaps, and the reading optical path is between the light-shielding plates, so that the illumination light is always It is possible to match the overlapping areas with high illuminance and the reading line, which is very effective.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of a document reading device embodying the present invention, and FIG. 2 is a cross-sectional view showing the configuration of a portion near the illumination light source of the document reading device according to the present invention. FIG. 3 is a schematic diagram showing the configuration of a conventional document reading device, and FIG. 4 is a sectional view showing the configuration near the illumination light source of the conventional document reading device. , 31.32...Pair of illumination light sources, 4,5.6...Reflection mirror, '7...
Reading series, 8... CCD line sensor, 9...
・Lighting light source cover, 101. '102...Pair of light shielding plates, ll...Reading optical path. Agent Patent Attorney Aihiko Fukushi (and 2 others) Figure 1 Figure 2 Tze Yg Figure 3 ll 4 ril

Claims (1)

[Claims] 1. In a document reading device that illuminates a document placed on a transparent plate with an illumination light source and reads information on the document line by line, a pair of illumination light sources for illuminating the document; and a pair of light-shielding plates provided opposite to the pair of illumination light sources for illuminating the original, with a reading optical path in between, the illumination light generated by the pair of illumination light sources generated on the part of the original to be read is A document reading device characterized in that the width of the overlapping portion is narrowed by the pair of light shielding plates.