JP2967361B2 - Document reader - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading apparatus that inputs image light of a document, converts a document image into a digital electric signal, and outputs the digital electric signal.

[Conventional technology]

In recent years, image processing has been added to a digital reading device that uses a fixed image sensor such as a CCD (Charge Coupled Device) to input image light from a document, convert the document image into a digital electrical signal, and output the digital electrical signal. 2. Description of the Related Art An image forming apparatus connected with an image processing apparatus for reproducing an image, such as a copying machine, has been developed. With the expansion of the functions, there is a strong demand for high image quality on the user side, and there is an increasing demand for higher accuracy of the document reading apparatus.

One of the methods is the instability of the light source for reading the original,
In order to correct variations in the characteristics of the reading sensor, etc., a standard white plate is provided immediately before reading the original, and the light reflected from the standard white plate is input to correct the correction data for the light source and reading sensor. I was getting it.

FIG. 7 is a side view of a main part of an example of a conventional document reading apparatus.
FIG. 8 is a plan view of the same.

The upper surface of the document reading apparatus main body A is covered with a document table glass 2 on which a document 1 is placed. Reference numeral 3 denotes a reading sensor unit, which is a combination of the solid-state imaging device 4 and the light source 5 as main components, and is slidably held on a guide rail 6 below the platen glass 2. The original is read by reciprocating right and left by a drive belt 8 driven by a pulse motor 7.

A standard white plate 9 is attached to the front or back of the platen glass 2 at a position earlier than the start of reading the original 1, that is, on the left side of the original 1 in FIG.
Starts scanning for reading the original, that is, starts moving rightward from the position shown in the figure, first, the reflected light from the standard white plate 9 is input, and the correction data of the image signal is captured.
Next, the original image signal read by moving the original 1 from the left end to the right end is corrected by the correction data.

In addition, in addition to the above example, the solid-state imaging device 4 is fixed inside the document reading apparatus main body A, and the light source 5 and the reflecting mirror are moved right and left along the guide rail 6 below the document table glass 2 as in the above example. There is also a configuration in which the original image is moved to form an image on the solid-state imaging device 4 by a reflecting mirror and an imaging lens disposed in the middle of the optical path.

[Problems to be solved by the invention]

However, in the above-mentioned prior art, correction data cannot be fetched during reading of a document, so that correction for instability, variation, etc. occurring during reading of a document is insufficient. For this reason, even when the correction is performed by the standard white plate 9, satisfactory image reproduction may not be actually achieved due to uneven light amount. In particular, there is a drawback that the density differs between the upper and lower portions (hereinafter referred to as back and front) of the original at the time of reading shown in FIG.

That is, when reading a document, the light source 5 and the solid-state imaging device 4 of the reading sensor unit 3 or only the light source 5 is moved along the document 1, but the guide rail 6 or the like to be moved is located at the back and front, or Due to the difference in height between the right and left sides, the conditions when reading the standard white plate 9 and the reading of the original 1 may be inconsistent, and in particular, the manufacturing may be performed even if the difference between the back and front is mechanically eliminated. Due to the above dimensional error, it is difficult to make the difference zero.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, and to provide a document reading apparatus capable of performing correction even during reading.

[Means for Solving the Problems] Therefore, a document reading apparatus according to the present invention includes a document table on which a document is placed, and a first white plate disposed outside the document placement position of the document table. A second and a third white plate arranged in parallel on both sides of the first white plate in a direction perpendicular to the longitudinal direction of the first white plate and narrowing the document placement position, and a document image placed on the platen; A line sensor that reads the first to third white plates and converts the read white image into an image signal; and a first white data obtained by reading the first white plate with the line sensor before reading the original image. ,
Correction means for performing shading correction on a document image signal based on second and third white data obtained by reading the second and third white plates with the line sensor while reading the document image. An object of the present invention is to achieve the above object by a configuration characterized by the above.

(Operation)

With the above configuration, it is possible to perform accurate shading correction on an image signal during reading of a document image.

〔Example〕

Hereinafter, an original reading apparatus according to the present invention will be described with reference to embodiments.

(First Embodiment) FIG. 1 is a plan view showing a main part of one embodiment of the present invention,
FIG. 2 is a perspective view of a main part of the embodiment, in which the platen glass is omitted. FIG. 4 is a block diagram showing a read signal processing unit. Parts that are the same as or correspond to those of the conventional example are denoted by the same reference numerals.

Reference numeral 9 denotes a standard white plate, and a platen glass 2 on which the original 1 is placed.
Inside the three sides of the original 1, that is, in the vicinity of the three sides of the original 1, in this embodiment, at a position before the start of the original reading, within a range corresponding to the vertical width of the original 1, the standard white plate 9-1 and the original reading Standard white plates 9-2 and 9-3 are attached to the platen glass 2 at positions not less than the horizontal length of the original, at the inner and lower positions of the original.

When the original 1 is exposed by a light source, for example, a halogen lamp 5, and the reflected light is read by the solid-state imaging device 4, first, the standard white plate 9-1 is read and the main scanning direction of the solid-state imaging device 4 is related.
The output correction data 11 is taken into the line memory 15. After that, the original 1 is read, and even when the original 1 is being read, the standard white plates 9-2 and 9-3 on the back and front sides are read, and the end white plate data 12 and 13 are taken in.
That is, mismatch and instability are detected. As described above, even while the original is being read, the original image signal 14 is corrected based on the input unevenness detected by the reflected light from the standard white plates 9-2 and 9-3 on both the front and rear sides, so that the original read signal is Unevenness can be corrected.

FIG. 3 shows a specific example of the correction. P ₁ is the input value before correction, that read bilateral, making pre-correction linear concluded example the far and effort a _1, a _2. Then make a correction line P ₂ which runs counter to the pre-correction linear P _1, the correction data in the line memory 15 obtained by reading the standard white plate 9-1 on the basis of the correction line ₂
The digital electric signal 14 of the original image is corrected in the shading correction circuit 16 in accordance with the corrected correction data.
The output unevenness is corrected.

(Second Embodiment) In the first embodiment, if the standard white plate 9-1 on the reading start side is continuous over the entire vertical width of the original 1, the standard on both sides of the original platen glass 2, that is, the back and front sides. White board 9-2,
9-3 can correct unevenness on both sides even if it is discontinuous.
The arrangement of the standard white plates 9-4 and 9-5 of the second embodiment is shown in FIG.

That is, even if it is non-continuous, the standard white plate 9-4, 9-5
In a place where there is no data, it is possible to perform correction with a certain degree of accuracy by using the data of the standard white plate before that.

(Third Embodiment) FIG. 6 shows a configuration in which the standard white plate 9-6 is provided at the rear end of the platen glass 2, that is, at the reading end side of the document 1, in addition to the configuration of the first embodiment. Standard white plate 9 in all four directions
This is an embodiment surrounded by -1,9-2,9-3,9-6.

In this case, after reading the original, the original illumination lamp 5
Since the correction is performed by reading the standard white plate 9-6 also at the rear end, there is an effect that the accuracy of the correction is improved as compared with the first and second embodiments.

In each of the above embodiments, the standard white plates 9-1 to 9
The material of −6 and the method of adding the output correction based on the reflected light from the standard white plates 9-1 to 9-6 are known from various configurations, and are not limited to specific ones.

〔The invention's effect〕

As described above, according to the present invention, it is possible to reliably follow a change in the shading state in the main scanning direction during reading of a document image, and perform accurate shading correction on the document image signal.

[Brief description of the drawings]

FIG. 1 is a plan view showing an essential part of a first embodiment according to the present invention, FIG. 2 is a perspective view of an essential part of the embodiment, in which a platen glass is omitted, FIG. FIG. 4 is a block diagram showing a read signal processing unit, FIG. 5 is an explanatory diagram of a standard white plate arrangement of the second embodiment, FIG. 6 is an explanatory diagram of a standard white plate arrangement of the third embodiment, and FIG. FIG. 8 is a plan view of a main part of a conventional example. 1 is a document, 2 is a platen glass, 3 is a reading sensor unit,
4 is a solid-state image sensor, 5 is a light source, 6 is a guide rail, 9, 9
-1,9-2,9-3,9-4,9-5,9-6 are standard white plates.

Claims (1)

(57) [Claims] An original table on which an original is placed; a first white plate disposed outside the original placing position of the original table; and the original in a direction orthogonal to a longitudinal direction of the first white plate. Second and third white plates arranged in parallel on both sides of a narrow mounting position, an original image mounted on the original platen, and the first to third white plates.
A line sensor that reads a white plate of the original into an image signal, first white data obtained by reading the first white plate with the line sensor before reading the original image, and reading the original image. Correction means for performing shading correction on a document image signal based on second and third white data obtained by reading the second and third white plates with the line sensor; Reader.