JPH0514714A - Picture data input device - Google Patents

Abstract

PURPOSE:To input picture data obtained from an original after correcting the variation of the picture data due to the difference from the light quantity of a white reference surface for shading correction and the surface of the original. CONSTITUTION:A light quantity difference correction coefficient setting part 16 to store light quantity difference correction data for correcting the picture data based on the difference of the quantities of light from the white reference surface and the surface of the original is provided. Then, the picture data outputted from a shading correcting means 12 is multiplied by a coefficient outputted from the above-mentioned correction coefficient setting part 15. A light quantity difference correcting arithmetic part 16 is a multiplying means for it, and the output data of this light quantity difference correcting arithmetic part 16 is inputted to a picture processing part 8 as the final picture data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data input device, and more particularly to an image data input device for shading-correcting and inputting image information read from a document.

[0002]

2. Description of the Related Art A digital copying machine or a facsimile machine has a reading device for reading image information from a document and an image information processing device for processing the read image information.

FIG. 4 is a diagram showing the configurations of the reading device and the image information processing device of the digital copying apparatus. In the figure,
The document 1 is conveyed in the direction of arrow B by a well-known feeding device (not shown). Then, when the end surface of the original 1 comes into contact with the ADF gate 2, the conveying operation is stopped, and the original 1 is set at a predetermined position on the platen glass 3 as shown in the drawing.

When the original feeding operation is stopped, the fluorescent lamp 4
The scanning unit 4 including a, the reflector 4b, and the mirrors 4c to 4e moves in the direction of arrow A to scan the surface of the document 1. By this scanning, the original 1
Reflected and scattered light of the light radiated toward is incident on the lens 5, reduced in size, and then condensed on the CCD image pickup device 6 a arranged on the board 6. The scanning unit 4
Is moved by a well-known drive device devised so that the length of the optical path 11 from the document 1 to the reduction lens is constant.

The image information sequentially output from the CCD image pickup device 6a is supplied to a shading correction circuit 7, and after a difference in photoelectric conversion characteristics, that is, shading is corrected,
It is input to the image processing circuit 8. When the reading of the image information is completed, the ADF gate 2 opens downward, and the document 1 is AD
It slips on the F gate 2 and is discharged.

Incidentally, the shading correction is generally corrected based on the density of the white reference plane read by the reading device. In the illustrated digital copying apparatus, a white reference surface (hereinafter simply referred to as a reference surface) 10 is formed by applying a white color to a predetermined area of the case 9 that holds the ADF gate 2.

Before reading the original 1, the density of the reference surface 10 is first read and stored in a predetermined storage means, and then input based on the difference between this value and the standard density of the reference surface 10 which is known in advance. The image information of the document 1 to be recorded is corrected.

[0008]

The above-mentioned prior art has the following problems.

As shown in FIG. 4, the surface of the original 1 and the reference surface 10 are displaced from each other by the thickness of the platen glass 3. That is, the fluorescent lamp 4a, the original 1 and the reference surface 10
There is a difference in their respective distances. As a result, fluorescent lamp 4
The amount of light emitted from a differs between the surface of the document 1 and the reference surface 10.

There is no practical problem if the difference in the light amount between the two is constant in the main scanning direction, that is, in the longitudinal direction of the fluorescent lamp 4a. However, in reality, the light amount distribution in the main scanning direction is not constant on the surface of the original 1 and the reference surface 10. Figure 5
Is a light amount distribution in the main scanning direction on the surface of the document 1 and the reference surface 10. In the illustrated example, the light amount difference is large at both ends in the main scanning direction, and the light amount difference is small near the center.

As described above, since the light quantity distribution in the main scanning direction is not constant on the surface of the original 1 and the reference surface 10,
The conventional apparatus that corrects only the difference in photoelectric conversion characteristics by shading correction has a problem that the density of the original 1 cannot be accurately reproduced.

An object of the present invention is to solve the above problems,
An object of the present invention is to provide an image data input device capable of correcting image information read from a document based on a difference in light amount distribution between the reference surface and the document surface and reproducing the density of the document with high accuracy.

[0013]

SUMMARY OF THE INVENTION To solve the above problems and to achieve the object, the present invention provides a light amount difference correction determined based on a difference in light amount distribution in the main scanning direction between a document surface and a reference surface. It is characterized in that it is provided with a light quantity difference correction data storage means for storing data in advance and a calculation means for correcting the image data output from the shading correction means with the light quantity difference correction data.

[0014]

According to the present invention having the above characteristics, the shading-corrected image data can be further corrected by the predetermined correction data, and the difference in the light amount distribution between the original surface and the reference surface in the main scanning direction is constant. Even if not done, the density of the original can be accurately reproduced.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing a main configuration of an image data input device showing an embodiment of the present invention, and the same symbols as in FIG. 4 are the same or equivalent parts.

In the figure, the data output from the CCD image pickup device 6a is supplied to a shading correction calculation unit 12 and a reference surface density read data storage unit 13. The data from the CCD image pickup device 6a stored in the reference surface density read data storage unit 13 is output to the correction coefficient generation unit 14 in response to the read signal.

The correction coefficient generator 14 generates a coefficient for correcting the input data to a predetermined white reference value.
The correction coefficient generator 14 can be composed of a ROM that generates a predetermined coefficient using the supplied data as an address.

The data output from the CCD image pickup device 6a is subjected to shading correction by the correction coefficient in the shading correction calculation section 12. The shading-corrected data is subjected to light amount difference correction in the light amount difference correction calculation unit 16 and output to the image processing unit 8.

In the light quantity difference correction calculation section 16, correction calculation is performed according to the correction coefficient supplied from the light quantity difference correction coefficient setting section 15. This light amount difference correction coefficient setting unit 15
It is composed of a ROM and stores a light amount difference correction coefficient for matching the light amount on the document surface with the light amount on the reference surface. The light amount difference correction coefficient is set for each bit in the main scanning direction based on the light amount difference between the document surface and the reference surface which is measured in advance.

The correction coefficients set in the correction coefficient generating section 14 and the light amount difference correction coefficient setting section 15 are shown in FIG.
Will be described later.

The image data input device having the above structure operates as follows. FIG. 3 is a flowchart showing the operation of this embodiment. First, in step S1, the scanning unit 4 is adjusted to the home position. The home position is a position where the light reflected by the reference surface 10 can be received by the mirror 4c.

In step S2, scanning of the scanning unit 4 is started in the direction of arrow A, that is, the sub-scanning direction,
In step S3, data is sequentially read from the CCD image pickup device 6a in the main scanning direction, and the shading correction calculation unit 1 is read.
2 and the reference surface density read data storage unit 13.

In step S4, it is determined whether the input of the density reading data of the reference surface 10 is completed, that is, whether the data for one line in the main scanning direction is stored in the reference surface density reading data storage unit 13.

If the determination in step S4 is affirmative, in step S5, the write (write) signal of the reference surface density read data storage unit 13 is stopped, and the read (read) signal is supplied to correct the reference surface density read data. Coefficient generator 14
Output to.

In step S6, a correction coefficient is read using the reference surface density read data as a read address, and shading correction is performed according to this coefficient.

In step S7, the light amount difference correction coefficient is read from the light amount difference correction coefficient setting unit 15, and in step S8, the light amount difference correction coefficient is corrected according to this coefficient.

Next, the correction coefficient will be described. FIG. 2 is a diagram showing an example of density reading data of the reference surface 10.
In the figure, the white reference value is "63", the black reference value is "0", and the density between white and black is represented by 64 gradations, that is, 6-bit data. The density read data xw of the reference surface 10 is “6” if there is no variation in photoelectric conversion characteristics.
It should be 3 ", but in practice, it deviates from the reference value as shown in the figure, and the deviation is usually different in the main scanning direction.

Therefore, the correction coefficient generator 14 generates a coefficient for correcting the reference surface density read data to the reference value, that is, "63". As understood from the figure, the reference surface density read data xw is set to the reference value “6”.
The coefficient for correcting to "3" can be calculated by (63 / xw). The correction coefficient generation unit 14 corresponds to 64 types of density data xw, respectively, and sets the white reference value “6”.
By storing the coefficient to be corrected to "3", a desired coefficient can be read using the supplied density data as an address.

Based on the same principle, the light amount difference correction coefficient is set to a value for correcting and matching the light amount difference between the original surface and the reference surface as shown in FIG.
However, since the correction coefficient for each bit (b1 to bn) in the main scanning direction is stored in the light amount difference correction coefficient setting unit 15, the density data supplied as described above may not be read as an address. Absent. Corresponding to the bit data sequentially output from the shading correction calculation unit 12, the correction coefficients from the first bit b1 to the nth bit bn are sequentially read and supplied to the light amount difference correction calculation unit 16.

In the above description, the coefficients are set so that the shading correction calculation unit 12 and the light amount difference correction calculation unit 16 perform multiplication to correct the input data. However, the shading correction calculation unit 12 and the light amount difference correction calculation unit 16 are calculation units that add input data,
Each coefficient may be set to a value such that the data can be corrected to a desired value by addition.

[0031]

As is apparent from the above description, according to the present invention, shading correction of image data can be performed, and image data generated by a difference in light amount between a reference surface and a document surface due to a difference from a light source. Can also be corrected. As a result, the accuracy of reproducibility of the original can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main function of an image input device showing an embodiment of the present invention.

FIG. 2 is a diagram showing an example of density read data of a white reference surface.

FIG. 3 is a flowchart showing the operation of the embodiment.

FIG. 4 is a block diagram showing a hardware configuration of an image data input device.

FIG. 5 is a diagram showing a light amount difference between a document surface and a reference surface.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Original document, 3 ... Platen glass, 4 ... Scanning unit, 5 ... Reduction lens, 6a ... CCD image pickup element, 12 ... Shading correction calculation section, 13 ... Reference surface density read data storage section, 14 ... Correction coefficient generation section,
15 ... Light amount difference correction coefficient setting unit, 16 ... Light amount difference correction calculation unit

Claims (1)

Claim: What is claimed is: 1. Image data for image input of a document, which is read based on the reflected and scattered light of a light source with which the document is irradiated, with shading correction based on the density data of the white reference plane. In the input device, a light amount difference correction data storage unit for storing in advance the light amount difference correction data determined based on the difference between the light amount distributions of the light sources in the main scanning direction on the white reference surface and the document surface, An image data input device, comprising: an arithmetic unit that corrects the image data output from the shading correction unit with the light amount difference correction data.