JPH04367164A - Manual multilevel picture input device - Google Patents

Abstract

PURPOSE:To obtain an accurate original reading data correcting function realizing high reproducibility of a original. CONSTITUTION:A page buffer 20 stores one page of original data 20c including standard density plate parts 20a and 20b read by the image sensor of the manual multilevel picture input device. A maximum/minimum value detection parts 21 detects the maximum and minimum values of the original data 20c. A correction processing control part 23 decides the density band of the applicable standard density plate part 20a based on the maximum and minimum values of the document data 20c and the known density data of the standard density plate part 20a, and prepares density correction formulas 25a to 25c based on the density of the density band and the reading density. The density of the standard density plate part 20b and original data 20c read from the page buffer 20 are corrected using the correction formula.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a manual multivalued image input device, and in particular, it corrects errors in image data due to unevenness in a light source or imaging system, as well as variations in photoelectric conversion characteristics between bits of an image sensor. The present invention relates to a manual multivalued image input device for inputting images.

0002

2. Description of the Related Art Main scanning is performed by receiving reflected and scattered light from the surface of a document with a one-dimensional image sensor (hereinafter simply referred to as an image sensor). Image input devices that perform sub-scanning by moving in a direction are widely used. Such image input devices include a shading correction device that corrects errors in document read data due to unevenness in the light source and imaging system, and variations in photoelectric conversion characteristics between bits of the image sensor.

In this shading correction, one density display plate is read prior to reading the original, and the original read data is corrected based on the read data and the difference in standard density of the density display plate that is known in advance. I was doing it.

By the way, some image input devices have a platen for placing an original, and others do not have a platen but have a handy scanner with a built-in image sensor placed directly on the original and manually move it. There is also a manual image input device that performs sub-scanning.

[0005] In an image input device having a platen on which a document can be placed, the density display plate is pasted or printed on the platen.

On the other hand, manual image input devices without a platen have the advantage that image information can be easily input regardless of the shape of the medium on which the image information is written or the position on the medium. Due to the structure, it is difficult to secure a place to provide the concentration display plate. Therefore, when reading a document using a manual image input device, the density of the margin area of the document is regarded as the standard density, and shading correction is performed based on the density of that area, or shading is corrected based on the fixed standard value set at the manufacturing stage. I was making corrections.

[0007]

[Problems to be Solved by the Invention] The above-mentioned prior art has the following problems. When obtaining binary data of a document using a manual image input device, there were no practical problems with the above shading correction method.

However, in recent years, there has been a demand for a multi-value image input device that can input multi-value data such as 64 gradations or 256 gradations and faithfully reproduce half-tone images. . In response to these demands, it has been difficult to accurately correct the halftone (gray) portions using the conventional method of correcting the document scan data using only the margins of the document, that is, the white information, as the standard density. . Furthermore, there is a problem in that correction using fixed standard values at the manufacturing stage cannot cope with changes in the optical system over time.

[0009] The purpose of the present invention is to solve the above problems,
It is an object of the present invention to provide a manual multi-value image input device having an accurate original read data correction function so as to obtain high reproducibility of the original even when inputting a multi-value image.

Another object of the present invention is to provide a manual multivalued image input device that is capable of highly accurate correction of read data of a document using a standard density plate extending in the sub-scanning direction.

[0011]

[Means for Solving the Problems] In order to achieve the above object, the invention of claim 1 provides a method for manually feeding an image sensor in the sub-scanning direction on a reading guide for each optical density in the sub-scanning direction. A first standard density display section having a plurality of density bands whose optical densities are varied in the main scanning direction and a second standard density display section which has a plurality of density bands whose respective optical densities are varied in the main scanning direction, respectively. The image sensor is provided along the main and sub-scanning directions of the image sensor, is read at the same time as the document is read, and is created based on the densities of the first and second standard density display sections stored in the page buffer and the difference between the respective standard densities. The present invention is characterized in that it is configured to correct the document read data by applying a correction formula based on the above.

The invention according to claim 2 is characterized in that original read data read in three primary colors and stored in page buffers for each color is corrected using a correction formula created for each color.

[0013]

[Operation] According to the invention of claim 1 configured as described above, after the first and second standard density display sections and the original read data are once stored in the page buffer, the original read data is stored in one raster. Firstly, the density can be corrected based on changes over time in the sensitivity of the lamp, optical system, and image sensor. Second, while the reading line is moving in the sub-scanning direction, the amount of light from the lamp that illuminates the document surface changes, the document is deflected, and the manual multilevel image input device moves in the sub-scanning direction. Even if the sensitivity of the image sensor changes per raster or per bit due to changes in CCD light accumulation time due to changes in speed, stable and reproducible data can be read across the entire document. .

Further, according to the second aspect of the invention, it is possible to obtain color document reading data that has been satisfactorily density-corrected.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 3(a) is a plan view of a manual multivalued image input device showing an embodiment of the present invention.

In the figure, the handy scanner 1 includes a lamp for illuminating the surface of a document 29, a reading element (image sensor) that receives reflected light of the light irradiated by the lamp, and an amount of movement of the handy scanner 1 in the sub-scanning direction. It has a built-in encoder (none of which is shown) for detecting. The output signals of the reading element, encoder, etc. are
It is connected to the control device 2 via a cable.

[0017] The reading guide 3 is attached to the handy scanner 1.
A vertical member 3a extends in the sub-scanning direction, and a horizontal member 3b perpendicular to the vertical member 3a extends in the main scanning direction, that is, the direction in which the reading elements are arranged. The overall shape is L-shaped.

The horizontal member 3b of the reading guide 3 has a first density display plate 4 extending in its longitudinal direction (main scanning direction).
is pasted. Further, a second density display plate 5 extending in the longitudinal direction (sub-scanning direction) is attached to the vertical member 3a.

In this example, the fracture position X-X is shown in FIG. 3(b).
As shown in the cross-sectional view at , the concentration display plate 5 is attached to the bottom step surface of the vertical member 3a, but it may be formed integrally with the vertical member 3a.

The first and second density display plates 4 and 5 have nine display marks ranging from black to white, as shown in an enlarged view in FIG. 3(c).
Density bands 41 to 49 and 51 to 59, each several mm wide (for example, 2 mm wide), each having a standard density of steps, are printed. These nine concentration bands are just an example, and the present invention is not limited thereto.

FIG. 4 is a block diagram showing the configuration of a control device according to an embodiment of the present invention.

As shown in the figure, this control device is controlled by a microcomputer (CPU) 6.
A program for operating U6 is stored in ROM7. The control device includes a data input circuit 8, a position detection circuit 9,
It includes a lamp control circuit 10, an image data output circuit 11, and a RAM 12 for data storage.

Image data read by the image sensor 13 is taken into the control device from the data input circuit 8, and is stored in the RAM.
12 is stored. The position detection circuit 9 is for detecting the position of the handy scanner 1 based on the amount of movement when the handy scanner 1 is reciprocated in the sub-scanning direction.
Scheduled processing is performed based on signals supplied from an encoder 14 built into the handy scanner 1. A lamp control circuit 10 controls lighting of a lamp (for example, an LED lamp) 15 that illuminates the original.

Furthermore, the image data output circuit 11 performs control to output the multi-valued image data processed by the control section to the outside.

Next, the image input operation of this embodiment will be explained. The image input operation includes an operation of reading the density of the density display plate 5 and an operation of reading the original density.

First, an outline of the image input operation will be explained. As shown in FIG. 3(a), the reading guide 3 is placed on the document 29 in preparation for the reading operation, and then the two sides of the handy scanner 1 are attached to the vertical member 3a and the horizontal member of the reading guide 3. 3b to determine the reading start position, that is, the home position of the handy scanner 1.

Next, the handy scanner 1 is put into operation, the density band 49 of the first density display plate 4 is set as the reading start position, and data is sequentially read up to the last position of the original 29 while moving in the sub-scanning direction. Read and write it to a page buffer, not shown. Next, a first correction formula is created based on the difference between the density data of the first density display plate 4 stored in the page buffer and the known density data, and this correction formula is used to calculate the first density data read from the page buffer. One line of original data including each density band of the second density display plate 5 is corrected.

Next, a second correction formula is created based on the difference between the corrected density data of each density band of the second density display plate 5 and the known density data, and this correction formula is used to Correct the original data.

The above correction processing is performed continuously for one page of the original. In this way, the correction of the document density read data is processed in real time for each reading line.

Next, the operation of the control device for image input will be explained in detail. FIG. 5 is a flowchart showing the image input operation.

In the figure, first, in step S1, the lamp 15 is turned on. When the light output of the lamp becomes stable, the process proceeds to step S2.

In step S2, one page of data including the first and second standard density plate portions 4 and 5 is read. The read density data of the first and second density display plates 4 and 5 and the document portion are stored in a predetermined storage area in the RAM 12 or in a page buffer (not shown).

Next, the process proceeds to step S3, where a first concentration data correction formula is calculated. In calculating this correction formula, as shown in FIG. 6, the maximum and minimum values of density are detected from the read data of one page of the original portion (step S31).
, from among the known concentration data of the first concentration display plate 4, a concentration band A that is equal to or greater than the maximum value and closest to it;
A density band B that is less than or equal to the minimum value and closest to it is determined (steps S32, S33). Next, a predetermined number of intermediate density bands are determined by equally dividing the plurality of density bands sandwiched between these density bands A and B (step S34). Then, the difference between the read data for each density band and the known density data of these density bands is detected, and a first correction formula is calculated based on this (step S
35).

In step S4, the second standard density plate portion 5 and one line of original data are read from the page buffer, and this read data is corrected according to the first correction formula.

In step S5, a second density data correction formula is calculated. As shown in FIG. 7, this correction formula is calculated from the read data of one raster document portion.
The maximum and minimum values of the concentration are detected (step S51), and the second
From among the known concentration data of the concentration display plate 5, a concentration zone C that is equal to or greater than the maximum value and closest to it, and a concentration zone D that is equal to or less than the minimum value and closest to it are determined (
Steps S52, S53). Then, these concentration bands C
, D are evenly divided to determine a predetermined number of intermediate density bands (step S5).
4). Then, the difference between the read data for each density band and the known density data of these density bands is detected, and a second correction formula is calculated based on this (step S35).
.

In step S6, one raster worth of the document data is corrected using the second correction formula. In this manner, when the density correction process for one raster of original data is completed, this original data is output to another device (not shown).

In step S8, it is determined whether correction of all document data has been completed. If the determination in step S8 is negative, the process returns to step S4, reads the density of the next reading line, and corrects it by repeating the above process.

In this way, the process continues until the determination in step S8 becomes affirmative, and correction of the image read data of the document is performed in real time in response to the reading operation.

The processing shown in FIGS. 6 and 7 will be specifically explained using FIGS. 8 and 9. Note that since the processes in FIGS. 6 and 7 are the same or equivalent, they will be described below using FIG. 6.

For example, as shown in FIG. 8, the maximum and minimum values of the reading density for one page of the original are respectively "5".
3" and "8" (step S31), the densities "55" and "7" of the density band of the first standard density plate 4 are determined in steps S32 and S33, respectively. Next, from the maximum and minimum concentrations "55" to "7",
If it has been determined in advance that two density bands are to be determined, then in step S34, the densities "39" and "23" of the density bands of the first standard density plate 5 are determined.

[0041] The process then proceeds to step S35, where a process of calculating a first correction formula is performed. That is, as shown in FIG. 9, concentration band number 2 of the standard concentration plate 5
, 4, 6, and 8 are the values shown in column A, and their read densities are 8, 25, 38, and 53, respectively, as shown in column B. 8～
25 to known concentrations 7-23, concentrations 26-38 to known concentrations 24-39, and concentrations 39-53 to known concentrations 40-
A correction formula moving to step 55 is calculated.

This correction formula is as follows.

Correction formula for transferring density values 8 to 25 to known density values 7 to 23 Correction value = 7 + (23-7) x (input data - 8) ÷ (25-8)
...(1) Correction formula for transferring the density values 26 to 38 to the known density values 24 to 39 Correction value = 24 + (39 - 24) x (input data - 26) ÷ (38
-26)...(2) Correction formula for transferring the density values 39 to 53 to the known density values 40 to 55 Correction value = 40 + (55 - 40) x (input data - 39) ÷ (53
-39)...(3) The method for correcting the original data has been explained above with reference to step S3 of FIG. 5, that is, FIG. 6, but the same method also applies to step S5 of FIG. The original data is corrected.

According to this embodiment, the maximum and minimum values of the density of the read data of the original are displayed on the density display plate 5, respectively.
Without forcibly correcting to white (density 63) and black (density 0), the density is adjusted to the maximum and minimum density values of the read data (in the above example, "55" and "7"). Since the read data can be corrected, the read data can be corrected with high precision.

Next, the operation of original data correction according to the present invention will be explained with reference to the functional block diagrams of FIGS. 1 and 2.

A page buffer 20 stores one page of data including the standard density plate portion read by the image sensor of the manual multivalued image input device 1. As shown in the figure, the page buffer 20 stores data 20c for one page of the original portion and read data 20a and 20b of the first and second standard density plates 4 and 5.

Reference numeral 21 denotes a maximum and minimum value detecting section that detects the maximum and minimum values of the density when the data 20c of the original portion is stored in the page buffer 20. 22 is a memory that stores known concentration data of the first standard concentration plate 4;

23 determines a density band to be used for correction processing from the maximum and minimum density values of the data 20c of the original portion detected by the maximum and minimum value detection section 21 and the known density data 22. , and then a correction processing control section that supplies data corresponding to the density band to a comparator and a correction formula, which will be described later. The correction processing control unit 23 mainly performs steps S32 to S in FIG.
35 processes are performed.

Comparators 24a to 24c determine the density range to which the read data of the document section read bit by bit from the page buffer 20 belongs. Comparator 24a~
The reference value 24c is set by the correction processing control section 23.

25a to 25c are the comparators 24a to 24
The correction equation is enabled by the output of c. For example, 25a is the correction formula (1), 25b is the correction formula (2), and 25c is the correction formula (3). Preferably, the format of the correction equation is stored in the correction equations 25a to 25c, and variables that change for each page of the correction equation are set for each page by the correction processing control section 23.

Now, the read data 2 of the second standard density plate 5 and the original portion stored in the page buffer 20
0b and 20c are read out one bit at a time in the main scanning direction,
The signals are sent to comparators 24a-24c. When the input data is 8≦input data≦25, the comparator 24a is turned on, and when the input data is 25<input data≦38, the comparator 24b is turned off when the input data is 25<input data≦38.
4c outputs, for example, a high level signal when input data is 38<input data≦53. Correction formula 25
When the comparators a to 25c receive high level signals from the comparators 24a to 24c, they become enabled and correct the density of one bit of the input read data 20b and 20c. The corrected data is sent to and stored in the line memory 30 of FIG. 2.

At this time, the maximum and minimum value detection section 31 detects the maximum and minimum values of the density of the read data 20c of the document portion. Similar to the correction processing control section 23, the correction processing control section 33 determines a density band to be used in the correction processing, and then supplies data corresponding to the density band to a comparator and a correction formula, which will be described later.

Next, one raster of original reading data 20c stored in the line memory 30 is read bit by bit and sent to comparators 34a to 34c. Comparator 34a
When input data is 8≦input data≦24, comparator 3
The comparator 4b outputs, for example, a high level signal when the input data is 24<input data≦39, and the comparator 34c outputs a high level signal when the input data is 39<input data≦54. The correction formulas 35a to 35c are enabled when they receive high level signals from the comparators 34a to 34c, and correct the density of 1 bit of the input read data 20c of the original portion. The corrected data is sent to the line memory 36 and temporarily stored. The corrected data stored in the line memory 36 is then transferred to another device (not shown).

As described above, when the correction processing in the main and sub-scanning directions for one raster of the document section is completed, the data of the next one raster is read out from the page buffer 20, and the same correction processing as described above is performed. executed repeatedly.

As described above, according to this embodiment, the first and second density display plates 4 , 5 is added, first, the first concentration display plate 4 performs the correction, thereby making it possible to perform the density correction based on the temporal change in sensitivity of the lamp, optical system, and image sensor. In addition, due to the correction by the second density display plate 5, while the reading line is moving in the sub-scanning direction, the amount of light of the lamp that illuminates the document surface may change, the document may be deflected, and manual multi-value image input may occur. Even if the sensitivity of the image sensor changes on a raster-by-raster or bit-by-bit basis due to a change in the light accumulation time of the CCD due to a change in the moving speed of the device in the sub-scanning direction, the density can be corrected. Therefore, according to the manual multivalued image input device of this embodiment, stable and reproducible data can be read over the entire document.

Furthermore, the maximum and minimum density values of the read data of the original are displayed on the first and second density display plates 4, respectively.
, 5, white (density 63) and black (density 0) are not forcibly corrected, but the density is corrected according to the maximum and minimum density values of the read data. Correction can be performed with high precision.

Next, a second embodiment of the present invention will be described. In this embodiment, the reading density of original data read into a page buffer by a color manual multi-value image input device is corrected in the same manner as in the first embodiment. The reading guide 4 shown in FIG. 3 is used as a reading guide for correcting the reading density.

FIG. 10 shows a flowchart of a process for correcting the density of color original data read into a page buffer by a color manual multivalued image input device.

[0059] In step S11, first the lamp is turned on,
When the amount of light becomes stable, the process proceeds to step S12. In step S12, the R, G, and B three-color image sensors read the first and second density display plates 4 and 5 and one page's worth of original data for each color. Stored in page buffer.

[0060] When all the data for one page is read in the above manner, the process advances to step S13 and the R, G, B
A first correction formula is created for each color. As shown in FIG. 11, this correction formula calculates the maximum and minimum density values of R, G, and B from the read data of one page of the original part.
(step S131), and from among the known density data on the first density display plate 4, a density band that is equal to or greater than the maximum value and is closest to it, and a density band that is equal to or less than the minimum value and is equal to this is detected. The closest density band is determined for each color of R, G, and B (steps S132, S133). Next, by equally dividing the plurality of density bands sandwiched between these density bands, a predetermined number of intermediate density bands are determined for each color of R, G, and B (step S134). Then, the difference between the read data for each density band and the known density data of these density bands is detected, and based on this, R,
A first correction formula is calculated for each color of G and B (step S1
35).

Next, proceeding to step S14, one raster of data including each of the density bands 51 to 59 of the second density display plate 5 is read out from the R, G, and B page buffers, respectively. The read data is temporary, R, G, B
are stored in line memories for each color, and then the first
Density correction is performed using the correction formula.

In step S15, second correction formulas for each color of R, G, and B are created. In calculating this correction formula, as shown in FIG. 12, the maximum and minimum density values are detected from the read data of one raster document portion of each color of R, G, and B (step S151), and the second Among the known density data of the density display plate 5, the density band that is equal to or greater than the maximum value and is closest to it, and the density band that is equal to or less than the minimum value and is closest to it, are selected as R, G, B. It is determined separately (steps S152, S153). Next, by equally dividing the plurality of density bands sandwiched between these density bands, a predetermined number of intermediate density bands are determined for each of R, G, and B (step S154). Then, the difference between the read data for each density band and the known density data for these density bands is detected, and based on this, a second correction formula is calculated for each of R, G, and B (step S155). .

In step S16, density correction is performed bit by bit using the second correction formula on one raster of the original data to which the first correction has been applied. In this way, when the correction of one raster worth of original data for each R, G, and B is completed, the process advances to step S17.
Corrected data for each color is output to other devices.

In step S18, it is determined whether all the data for one page of the original has been corrected. If this determination is negative, the process returns to step S14 and the next R, G
, B. The density correction process for one raster of document data for each color is repeated.

As a result of repeating the above processing, if the determination in step S18 becomes affirmative, the series of processing described above ends.

As is clear from the above description, according to this embodiment, density correction due to changes over time in the sensitivity of the lamp, optical system, and image sensor, deflection of the original due to scanning the original, It is possible to read high-quality, reproducible color original data that has been subjected to density correction for changes in the light accumulation time of the CCD due to changes in the moving speed in the sub-scanning direction of the manual multi-level image input device. .

In each of the embodiments described above, the density of the original data was corrected using the first and second density display plates 4 and 5, but the present invention is not limited to this, and the density display of either one The density may be corrected using a plate.

[0068]

According to the invention of claim 1, the first and second density display plates are displayed on the first and second density display plates for original data read into the page buffer while moving the manual multivalued image input device in the sub-scanning direction. Since the correction based on the image density is applied, first, correction using the first density display plate allows density correction based on changes over time in the sensitivity of the lamp, optical system, and image sensor. In addition, due to the correction by the second density display plate, while the reading line is moving in the sub-scanning direction, the amount of light of the lamp that illuminates the document surface may change, the document may be deflected, or the manual multi-value image input device may Due to changes in the light accumulation time of the CCD due to changes in the moving speed in the sub-scanning direction, the sensitivity of the image sensor may vary per raster or per raster.
Even if the density changes bit by bit, the density can be corrected. Therefore, according to the manual multivalued image input device of this embodiment, stable and reproducible data can be read over the entire document.

Furthermore, the maximum and minimum density values of the read data of the original can be adjusted to the white (density 63) and black (density 0) of the first and second density display plates, respectively, without forcibly correcting them. Since the density is corrected according to the maximum and minimum density values of the read data, the read data can be corrected with high accuracy.

According to the second aspect of the invention, the same effect as the first aspect of the invention can be obtained for color read data of a document.

[Brief explanation of the drawing]

[Fig. 1] A first functional block diagram of an embodiment of the present invention.
FIG.

[Fig. 2] Second functional block diagram of an embodiment of the present invention
FIG.

FIG. 3 is a plan view of a manual multivalued image input device and a reading guide according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a schematic hardware configuration of a manual multivalued image input device.

FIG. 5 is a flowchart for explaining the operation of the first embodiment of the present invention.

6 is a flowchart showing details of step S3 in FIG. 5. FIG.

7 is a flowchart showing details of step S5 in FIG. 5. FIG.

FIG. 8 is an explanatory diagram of a specific example of steps S3 and S5.

FIG. 9 is an explanatory diagram of a specific example of calculation of a correction formula.

FIG. 10 is a flowchart for explaining the operation of the second embodiment of the present invention.

11 is a flowchart showing details of step S13 in FIG. 10. FIG.

12 is a flowchart showing details of step S15 in FIG. 10. FIG.

[Explanation of symbols]

1...Manual multivalued image input device, 3...Reading guide, 4,
5...First and second density display plates, 20...Page buffer, 21, 31...Maximum and minimum value detection units, 23, 33...
Correction processing control unit, 24a to 24c, 34a to 34c... Comparator, 25a to 25c, 35a to 35c... Correction formula, 30
, 36... line memory.

Claims (2)

[Claims] 1. A handy scanner having a one-dimensional image sensor that receives reflected and scattered light from a document is configured to perform sub-scanning by manually feeding it in a direction perpendicular to the main-scanning direction of the one-dimensional image sensor. In the manual multivalued image input device, the one-dimensional image sensor is provided along the main scanning direction of the one-dimensional image sensor on the reading guide for smoothly manual feeding of the handy scanner, and the optical density of each is varied in the sub-scanning direction. a first standard density display means having a plurality of density bands arranged along the sub-scanning direction;
a second standard density display means having a plurality of density bands whose respective optical densities are changed in the main scanning direction; and density bands of the first and second standard density display means read by the one-dimensional image sensor. and a page buffer for storing original density data; a density band of the first standard density display means used for correction is determined from the maximum and minimum values of the original density data, and the read density and density of the determined density band are determined. a first correction formula calculation means for calculating a first correction formula for correcting the read original density data based on a known difference in density;
a correction means for correcting one raster of original density data including a plurality of density bands of the second standard density display means using the first correction formula; Determining a density band of a second standard density display means used for correction, and calculating a second correction formula for correcting the document density data based on the difference between the read density of the determined density band and the known density. a second correction formula calculation means for calculating the second correction formula;
1. A manual multi-valued image input device comprising processing means for correcting the corrected document density data using the correction formula. 2. A handy scanner having a color one-dimensional image sensor that receives reflected and scattered light from a document is configured to perform sub-scanning by manually feeding the one-dimensional image sensor in a direction perpendicular to the main scanning direction of the one-dimensional image sensor. In the manual multivalued image input device, a reading guide for smoothly manual feeding of the handy scanner is provided along the main scanning direction of the one-dimensional image sensor, and each optical density is set in the sub-scanning direction. a first standard density display means having a plurality of density bands with varying optical densities; and a second standard density display means provided along the sub-scanning direction and having a plurality of density bands with respective optical densities varied in the main scanning direction. a standard density display means, a page buffer for three primary colors that stores density bands of the first and second standard density display means and original density data read by the one-dimensional image sensor, and a page buffer for each of the three primary colors; The density band of the first standard density display means used for correction is determined for each color from the maximum and minimum values of the original density data, and the reading is performed based on the difference between the read density of the determined density band and the known density. a first correction formula calculation means for calculating a first correction formula for each of the three primary colors for correcting the original density data;
a correction means for correcting the document density data of each of the three primary colors of one raster including a plurality of density bands of the second standard density display means using the first correction formula; , determines the density band of the second standard density display means used for correction for each color from the minimum value, and corrects the document density data based on the difference between the read density of the determined density band and the known density. The present invention is characterized by comprising a second correction formula calculation means for calculating a second correction formula for each color, and a processing means for correcting the corrected document density data for each color using the second correction formula. Manual multivalued image input device.