JP3150033B2 - Color scanner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color scanner. More specifically, the present invention relates to a color scanner which operates stably without being affected by environmental conditions such as temperature, and satisfactorily correcting performance fluctuations with a short period.

[0002]

2. Description of the Related Art In recent years, a color scanner has been frequently used to input a color image into a computer. However, when a color original is read by a color scanner, stable image data is not always obtained.
This is because the characteristics of a light source such as a fluorescent lamp used in a color scanner fluctuate under the influence of ambient temperature, temperature change due to self light emission, voltage fluctuation, and the like. further,
This is also because the image reading performance of the color scanner fluctuates finely every time an image is read because a performance change or a mechanical change over time of the sensor occurs.

FIG. 10 schematically shows how the performance of the color scanner varies as described above. In the figure, the vertical axis represents "performance" having no specific unit, and the horizontal axis represents the passage of time. In FIG. 10, each time from the time point a to the time point b, from the time point b to the time point b ', and from the time point b' to the time point b "displayed on the horizontal axis is necessary for reading one image. The time from the time point a to the time point c represents a long time such as one year, for example, and the color scanner at each of the time points a, b, and c. Are represented by d, e, and f, respectively.

[0004] In addition to the color scanner, the performance of the device is generally converted as shown in FIG. That is, the change in performance is classified into the following three. (1) Significant performance degradation due to accumulation of performance degradation from high initial performance d immediately after the start of use over a long period of time, such as from point a to point c. (2) Performance change that gradually decreases during the operation of reading one image, such as from time a to time b, from time b to time b ', and from time b' to time b ". (3) Time a From time point b to time point b ', from time point b' to time point b ", a performance change that fluctuates randomly and finely within the time for reading one image.

The above three performance change states are caused by the relationship between the time required to read one image and the cycle of the performance change. That is, the performance change (1)
This occurs when the cycle of performance fluctuation is sufficiently long compared to the time required to read one image. In this case, the change gradually occurs in the long term. The performance change (2) is 1
This occurs when the time required to read one image and the cycle of performance fluctuation are substantially the same. In this case, a change occurs gradually during the operation of reading one image. Also,
The performance change (3) occurs when the cycle of the performance change is sufficiently shorter than the time required to read one image.
In this case, a small change occurs in a cycle sufficiently shorter than the time for reading one image. Below, for convenience, performance changes
(1) is called a long-term performance change, performance change (2) is called a medium-term performance change, and performance change (3) is called a short-term performance change.

Next, each performance variation will be considered in more detail.
First, the above-described long-term performance fluctuation is characterized in that the cycle of the fluctuation is long. For example, a performance variation in units of time required for one image scanning period from time point a to time point b is a slight performance variation such as performance d → performance e and can be almost ignored in many cases. However, the performance fluctuation when the performance fluctuates little by little over a long time, such as a long-term performance fluctuation such as one year, is a large performance fluctuation such as performance d → performance f and cannot be ignored.

Next, the above-mentioned medium-term performance fluctuation has two fluctuation patterns. The first pattern is a pattern in which the performance gradually decreases, such as performance d → performance g, during a period of reading one image from time point a to time point b. The second pattern includes reading of the first image from time point a to time point b, reading of the second image from time point b to time point b ′, and reading of three images from time point b ′ to time point b ″. In reading the image of the eye, the corresponding time in each reading period (for example, the starting times a, b,
This is a pattern in which the performance in b ′) decreases over time, such as (for example, performance d → performance e → performance e ′).

Further, the short-term performance fluctuation is characterized in that the fluctuation cycle is shorter than the time required to read one image, and the cycle and the fluctuation direction are completely random.

The performance fluctuations described above cause the following inconvenience in the read image data. For example, when a long-term performance fluctuation occurs in the color scanner, when an image is read after a long time such as one year, for example, a color difference or the like occurs in both image data obtained even when the same image is read. Inconvenience occurs.
In addition, when the first pattern of the above-mentioned medium-term performance fluctuation occurs, there is a disadvantage that colors are different before and after one image. Further, when the second pattern occurs,
When reading multiple images consecutively, the first image →
There is an inconvenience that the color gradually changes from the second image to the third image and so on. In addition, when the short-term performance fluctuation occurs, the color is slightly different for each scanning line in one read image, and in the worst case, there is an inconvenience that the image is deteriorated because it looks like a stripe. Occurs.

Such performance fluctuations are caused by fluctuations in the electric circuit, mechanical structure, optical elements, etc. of the scanner head due to fluctuations in the power supply voltage and temperature.

For example, the above-mentioned long-term performance fluctuations include changes in performance over time of light sources and sensors, changes in driving conditions due to mechanical wear, and changes in the relative positional relationship and angle between the original and the scanner head. Caused by for that reason,
Average performance degradation gradually occurs during long-term use.

Further, in the above-mentioned medium-term performance fluctuation, the first
Before using the color scanner, the temperature of the scanner, which had been in a steady state in equilibrium with the ambient temperature before using the color scanner, increased by using the color scanner. This is caused by a gradual decrease in element performance on average. In order to return the scanner temperature to the ambient temperature before use (that is, a steady state) between the end of one image reading and the start of the next image reading, the performance in each image reading period is set. The change becomes a sawtooth. In the second pattern, the scanner temperature does not completely return to the ambient temperature before use between the end of one image reading and the start of the next image reading. This is caused by the fact that the performance at the start time points a, b, b ′ gradually decreases with time. in this way,
The performance of the light source and sensor changes as the ambient temperature changes.

The short-term fluctuations in performance include changes in the performance of light sources and sensors due to sudden fluctuations in power supply voltage and environmental temperature that occur randomly, backlash of mechanical parts such as gears and belts, and sliding parts. This is caused by fluctuations in various conditions that occur slightly every time use, such as fluctuations in the relative positional relationship and angle between the scanner head and the document due to fluctuations in driving conditions due to backlash and the like.

An example of a change in the relative angle between the scanner head and the document due to a change in the driving conditions due to the play of the sliding portion will be described below. FIG. 11 schematically shows the structure of the color scanner. The light source 2, the sensor 3, and the lens 4 are incorporated in the scanner head 1. The light emitted from the light source 2 is reflected by the original 5, and then condensed by the lens 4 to be incident on the sensor 3. Then, photoelectric conversion is performed by the sensor 3. At this time, the scanner head 1 moves on the rails 7 by the driving systems 6 and 6 to scan the document 5 in the sub-scanning direction.

Here, if play occurs due to mechanical play or wear at the sliding portion between the rail 7 and the drive system 6, 6,
As shown in FIG. 12, the angle between the scanner head 1 and the document 5 changes. Since such a change is caused by mechanical play, it occurs irregularly each time the scanner head 1 performs sub-scanning once. As a result, manuscript 5
, The incident angle of light with respect to the document 5 changes irregularly, and the intensity of the reflected light from the document 5 also changes irregularly during the sub-scan (each main scan). Thus, random short-term performance fluctuations occur.

Various techniques have been conventionally proposed as techniques for obtaining appropriate image data even if the characteristics of the color scanner change due to the performance fluctuations of the various color scanners described above (Japanese Patent Application Laid-Open No. 59-1984). No. 163968,
JP-A-61-290866, JP-A-62-101
181 and JP-A-62-92657).

These techniques generally include a reference image placed within the reading range of the image sensor, reference data obtained by color-separating the reference image in advance, and color correction means.
A means for comparing image data obtained from a reference image with the reference data when the apparatus is used, and determining a constant used for correction by the color correction means; Then, the reference image is scanned in advance during calibration of the apparatus, or the reference image is scanned in advance before scanning the original when the apparatus is used, and the obtained image data is compared with the above-described reference data which is separately stored in the apparatus. The fluctuation of the performance from the standard state is grasped, and this performance fluctuation is corrected by the above-mentioned color correction means by an appropriate method.

Hereinafter, each technique will be briefly described.
First, the "color system" disclosed in Japanese Patent Application Laid-Open No. 59-163968 is provided with a device calibration mode, and performs calibration of the device using the reference image every time the user designates the transition to the device calibration mode. It is configured to do so.

The "color image processing apparatus" disclosed in Japanese Patent Application Laid-Open No. 61-290866 has a gray chart arranged in the main scanning direction of the scanner or in a direction perpendicular to the main scanning direction. The gray chart is once scanned to correct the color variation in each scan and the color variation for each image to stabilize the performance of the scanner.

In the "color image processing apparatus" disclosed in Japanese Patent Application Laid-Open No. 62-101181, a color sample is arranged adjacent to a white reference plate of a scanner. Then, a color correction coefficient is calculated based on an image signal obtained by scanning the color sample every time an image is read, and the calculated color correction coefficient is stored in a storage unit provided in the color correction circuit. The image information obtained by scanning the document is corrected by a color correction circuit using the stored color correction coefficients.

In the "image input apparatus" disclosed in Japanese Patent Application Laid-Open No. 62-92657, an appropriate standard chart is arranged at both ends of a one-dimensional sensor head of a scanner toward the sensor side, and the standard image is always read. By reading the chart,
The scanner is configured so that the performance fluctuation of the scanner caused by the brightness of the fluorescent lamp during scanning and the performance fluctuation of the sensor is corrected in the next stage to stabilize.

In addition to the above-mentioned several technologies,
Techniques such as -60151 have been reported, but are generally similar.

Next, the prior art will be described in detail with reference to the "color image processing apparatus" disclosed in Japanese Patent Laid-Open No. 62-101181. FIG. 13 is a schematic configuration diagram of the color image processing apparatus. The color image processing apparatus includes a platen 11, an optical system 12, a quantizer 13, a RAM (random access memory) 14, a white balance circuit 1,
5. Corrector 16, gamma corrector 17, timing control circuit 18, color correction circuit 19, and CPU (central processing unit)
20.

In the vicinity of the document 21 on the document table 11, a white reference plate 22 having a white plate which is scanned before the document 21 is scanned and at least red, green and blue (hereinafter, R, G, B) are placed on the color sample 23 in which three or more colors are arranged. The optical system 12 includes a light source 24 for illuminating the white reference plate 22, the color sample 23 and the original 21 by sub-scanning movement in parallel with the original table 11, and an image sensor to which reflected light of the light from the light source 24 enters. 25. Then, the quantizer 13 quantizes the output signal from the image sensor 25 to n bits, and the optical system 12
The image data obtained when the white plate is scanned is stored in RAM1
4 is stored.

The white balance circuit 15 includes a RAM
After performing white balance adjustment based on the image data of the white reference plate 22 stored in 14, the optical system 12 scans the color sample 23 and the original 21 to obtain a white balance of the image data obtained. The image signal after the white balance is obtained in this way is sent to the corrector 16 and the RAM 1
4, shading distortion is removed based on the image data. The gamma corrector 17 receives the image signal output from the corrector 16 and corrects the gamma characteristic of the image data. The timing control circuit 18 controls the operation timing of the color correction circuit 19 based on the basic clock. Then, the CPU 20 controls the color correction circuit 19 to calculate and obtain the color correction coefficient.

The color correction circuit 19 includes a gamma corrector 17
Latch circuits 27, 28, and 29 for latching n-bit image data output from the CPU for each of the three colors RGB, and a RAM 30 for storing color correction coefficients calculated by the CPU 20,
A three-state buffer circuit 31 for writing signals to the RAM 30 and three RGB signals output from the RAM 30
Latch circuits 32, 33, and 34 for latching each of the color correction coefficients corresponding to the colors; n-bit image data latched by the latch circuits 27, 28, and 29;
Multipliers 35, 36, 37 for multiplying the color correction coefficients latched by the multipliers 3, 34, an adder 38 for adding output data from the multipliers 35, 36, 37, A latch circuit 39 for latching the output for each of the three colors RGB
40, 41. Then, the latch circuits 39, 40, 4
1 outputs an image signal composed of RGB image data.

The color image processing apparatus having the above configuration operates as follows. Prior to scanning of the original 21, the white plate of the white reference plate 22 is scanned by the optical system 12, and the image data obtained by the quantizer 13 is stored in the RAM 14. Next, while moving the optical system 12 in the sub-scanning direction toward the color sample 23 or the document 21, the white balance circuit 15 executes the color sample 23 or the document 21 to be executed later based on the image data stored in the RAM 14. The gain of the circuit is adjusted so that white balance can be achieved during scanning.

Here, the gain adjustment by the white balance circuit 15 is adjusted so that the image data obtained when the white plate of the white reference plate 22 is scanned becomes equal for each of the RGB colors. For example, if R image data> G image data = B image data, the circuit gain related to the R image data is reduced so that R image data = G image data = B image data. It is. However, to what extent the gain should be adjusted for each of the RGB image data values,
It is determined in advance. Thus, the white balance is obtained by inputting the image data obtained when the color sample 23 and the original 21 are scanned into the white balance circuit 15 after the circuit gain is adjusted for each color.

Next, the color balance is adjusted. For this purpose, the color sample 23 is scanned before the original 21 is scanned by the optical system 12, and image data corresponding to each color sample 23 is obtained by the quantizer 13. The image data corresponding to each of the obtained color samples 23 is white-balanced by the white balance circuit 15, shading distortion is removed by the corrector 16, and the gamma characteristic is corrected by the gamma corrector 17. It is.
Then, a matrix coefficient as the color correction coefficient is calculated.

The calculation of matrix coefficients by the CPU 20 at this time is performed as follows. Now, a red color sample among the color samples 23 is scanned and image data R2r,
It is assumed that G2r and B2r are obtained. Here, the appropriate image data obtained from the red color sample is R3r, G3r,
Assuming that B3r, the red correction coefficient is obtained by calculating a matrix coefficient composed of Mr11 to Mr33 satisfying the expression (1).

(Equation 1)

Then, by using the inverse matrix, necessary matrix coefficients can be obtained as shown in equation (2).

(Equation 2)

In the same manner, respective matrix coefficients are calculated using image data for each color obtained by scanning green and blue color samples. The obtained matrix coefficients for each color are averaged to obtain the color correction coefficient M1.
1 to M33 are obtained and stored in the RAM 30 via the three-state buffer circuit 31.

Next, the original 21 is scanned by the optical system 12, and RGB image data is obtained by the quantizer 13. Then, the obtained image data is white-balanced by a white balance circuit 15, shading distortion is removed by a corrector 16, and a gamma characteristic is corrected by a gamma corrector 17. 28 and 29 are sequentially latched.

At this time, the latch is performed at the timing shown in FIG. That is, in a one-line main scanning section as shown in FIG. 14A, the gamma corrector 17 sends out n-bit quantized image data of RGB in RGB units as shown in FIG. 14B. Every,
At the timings shown in FIGS. 14 (c) to 14 (e), each is latched by the latch circuits 27, 28, 29 of the color correction circuit 19.

Next, each of the image data (for example, R1, G1, B1) latched by the latch circuits 27, 28, 29 and the color correction coefficients M11 to M3 stored in the RAM 30.
3 and the corrected image data R0, G0, B0
It is determined by (3).

(Equation 3)

The above-described color correction is actually performed by the color correction circuit 1.
9 is performed as follows. That is, FIG.
4 (f), the color correction coefficient M1 of the color correction coefficients M11 to M33 stored in the RAM 30 is stored.
x (x = 1 to 3) is read out and the latch circuits 32, 33, 3
4 latched. At this time, the image data R1 is latched by the latch circuit 27, and the image data G1 is latched by the latch circuit 2.
8 and the image data B1 is latched by the latch circuit 29, the correction coefficient M11 is latched by the latch circuit 32, and the correction coefficient M1 is latched by the latch circuit 33.
2 is latched, and the correction coefficient M13 is latched in the latch circuit 34. Then, the multiplication (M1) is performed by the multiplier 35.
1 * R1), and multiplication (M12 *
G1), and multiplication (M13 * B
1) is performed.

Each multiplication result thus obtained is added to an adder 38.
And the operation value M11 * R1 + M12 * G1 + M13 * B1 is obtained, and is latched by the latch circuit 39 as corrected image data R0.

Next, at the timing shown in FIG. 14 (f), the color correction coefficient M2x (x = 1 to 3) is read from the RAM 30 and latched by the latch circuits 32, 33 and 34.
Then, the multiplication (M21 *) is performed by the multipliers 35, 36, and 37.
R1), (M22 * G1), and (M23 * B1) are performed and added by the adder 38 to obtain an operation value M21 * R1 + M22 * G1 + M23 * B1, which is latched in the latch circuit 40 as corrected image data G0. Is done. Further, the color correction coefficient M3x (x = 1 to 3) is latched at the timing shown in FIG. 14 (f), multiplied by the multipliers 35, 36 and 37, added by the adder 38, and added to the operation value M31 *. R1 + M32 * G1 + M33 * B1 is obtained and latched by the latch circuit 41 as corrected image data B0.

Thus, the latch circuits 39, 40, 41
The corrected image data R0 = M11 * R1 + M12 * G1 + M13 * B1 G0 = M21 * R1 + M22 * G1 + M23 * B1 B0 = M31 * R1 + M32 * G1 + M33 * B1 are shown in FIGS. 14 (g) to 14 (i). It is output at the timing shown.

As described above, color scanners are roughly classified into three types of performance fluctuations: long-term performance fluctuations, medium-term performance fluctuations, and short-term performance fluctuations. The following describes how the conventional image processing apparatus having a performance fluctuation correction function represented by the color image processing apparatus shown in FIG. 13 copes with these performance fluctuations.

First, it can be said that the long-term performance variation is an average performance variation in which the cycle of the variation is sufficiently long when the time required to read one image is set as a unit time. On the other hand, in the image processing apparatus having the above-described conventional performance fluctuation correction function, each time an image is read (that is,
By scanning a reference color chart or the like (for each unit time), the performance fluctuation is corrected based on the obtained image data. That is, as shown in FIG. 15 (corresponding to FIG. 10), the performance variation is corrected at each image reading start time a, b, b ′, b ″,. Thus, the performance is restored to the performance d.Therefore, even if a long-term performance fluctuation occurs, the performance fluctuation is sequentially corrected for each image reading.

In the above-mentioned medium-term performance fluctuation, the second
(The performance degradation at the start of each image reading when images are continuously read) has a fluctuation cycle substantially equal to the unit time. Therefore, also in this case, as described above, the performance fluctuation is corrected at each image reading start time a, b, b ', b ",... And the initial performance d is compensated, so that the correction is reliably performed. Will be.

[0043]

In the conventional image processing apparatus having the function of correcting the performance fluctuation, the performance fluctuation is corrected each time the image reading is started. The performance fluctuation is effectively corrected when the time fluctuation is large or substantially equal to the time (that is, in the case of the long-term performance fluctuation or the second pattern in the medium-term performance fluctuation). However, if the period of the fluctuation is smaller than the unit time,
(In other words, in the case of the first pattern (performance degradation during reading of one image) in the medium-term performance variation or in the case of short-term performance variation), performance degradation occurs during the correction cycle. However, there is a problem that the performance fluctuation is not corrected at all.

As described above, the first pattern and the short-term performance fluctuation in the above-described medium-term performance fluctuation are performance fluctuations caused by temperature fluctuations due to voltage fluctuations and heat generation of each unit during reading of one image. . When such performance fluctuations occur, there are problems such as different colors in the upper and lower portions of a single read image, or deterioration in image quality, resulting in an image having a rainbow shape.

The short-term fluctuations in performance also occur due to mechanical rattling that occurs during sub-scanning, such as rattling of sliding portions in the scanner head. The performance fluctuation at that time appears completely independently for each scanning line with each sub-scanning, and occurs randomly at an early period. When such a performance variation occurs, an image has a slightly different color for each scanning line, and in a severe case, the image looks like a horizontal line and the image quality deteriorates.

The following describes how the first pattern in the medium-term performance variation and the short-term performance variation as described above are handled by the conventional image processing apparatus having the performance variation correction function. I will tell you. First, Japanese Patent Laid-Open
"Color system" disclosed in JP-A-9-163968
Provides a device calibration mode, and calibrates the device when the user designates transition to the device calibration mode. In other words, this "color system" is designed to allow the user to specify the transition to the device calibration mode, and since the correction for performance fluctuations that occur once after the transition to the device calibration mode is not performed, It can be said that this is intended to correct the long-term performance fluctuation. Therefore,
In the present “color system”, it is impossible to correct the performance fluctuation of the first pattern or the short-term performance fluctuation in the medium-term performance fluctuation.

A "color image processing apparatus" disclosed in Japanese Patent Application Laid-Open No. 61-290866 scans a gray chart arranged in the main scanning direction of the scanner or in a direction perpendicular to the main scanning direction at the start of image reading. I am trying to do it. Therefore, although the performance at the time of scanning the gray chart is compensated, the correction for the performance variation caused after scanning the gray chart is not executed, and the first variation in the medium-term performance variation that occurs when an image is actually read is performed. It is not possible to correct the performance fluctuation of the pattern or short-term performance fluctuation. Similarly, Japanese Patent Application Laid-Open No. 62-101181
The "color image processing apparatus" (see FIG. 13) disclosed in Japanese Patent Application Laid-Open Publication No. H11-26095 scans a color sample 23 every time an image is read to obtain a color correction coefficient, and converts the image data obtained at the time of original reading into the color correction coefficient. The correction is made by using the above. Therefore, although the performance at the time of scanning the color sample 23 is compensated, no correction is made for the performance variation that occurs after the color sample scanning. Therefore, it is not possible to correct the performance fluctuation of the first pattern or the short-term performance fluctuation in the medium-term performance fluctuation that occurs when reading the document.

That is, in the above-described image processing apparatus having the function of correcting performance fluctuations, changes in voltage and environmental temperature, temperature rise due to heat generation of the apparatus itself, and document and scanner head due to mechanical backlash. It is impossible to correct short-term performance fluctuations that occur during the reading of one image due to fluctuations in the positional relationship between the two.

An "image input apparatus" disclosed in Japanese Patent Application Laid-Open No. 62-92657 has a standard chart arranged at both ends of a one-dimensional sensor of a scanner with the sensor side facing the light source and a sensor. It has a structure integrated with. Therefore, the fluctuation of the brightness of the light source and the fluctuation of the sensitivity of the sensor which occur during reading of one image can be corrected for each scanning line. However, as described above, since the standard chart is integrated with the light source and the sensor, the performance fluctuation caused by the fluctuation of the positional relationship between the original and the scanner head due to mechanical backlash is completely eliminated. It is defenseless.

As described above, in a conventional image processing apparatus having a function of correcting performance fluctuation, the performance fluctuation at the time of scanning a reference color chart or the like is generally corrected. No correction can be made for the performance fluctuation of the first pattern or the short-term performance fluctuation in the medium-term performance fluctuation occurring during reading.

Accordingly, an object of the present invention is to provide a color scanner capable of correcting in real time performance fluctuations that occur each time an image of one scanning line is read due to fluctuations in the performance of an optical system or fluctuations in mechanical driving conditions. Is to do.

[0052]

According to a first aspect of the present invention, a document placed on a document table is scanned by a scanner head to obtain color image data by photoelectric conversion means. In color scanners,
A color chart plate installed on the document table extending in the sub-scanning direction along a side edge on the main scanning start side of the document and the scanner head performs main scanning of the document for one scanning line. At this time, a latch circuit for holding image data obtained by main scanning of the color chart plate for one main scanning period prior to main scanning of the original document is associated with a selected address, and the performance fluctuation of the scanner head is changed. A plurality of look-up tables in which performance fluctuation correction data for correcting fluctuations in image data caused by the main scanning are written for each main scan, and image data of the color chart plate held in the latch circuit. A specific look-up table is selected as an address, and from the address specified by the image data of the original from the photoelectric conversion means in the selected look-up table. It is characterized by having a performance variation correction circuit for outputting read performance variation correction data of the image data.

According to a second aspect of the present invention, there is provided a color scanner in which a document placed on a document table is scanned by a scanner head to obtain color image data by photoelectric conversion means. A color standard plate that extends in the main scanning direction along the edge of the document plate and is provided on the platen, and has at least a red, green, and blue reference color chip;
A color chart plate provided on the platen and extending in the sub-scanning direction along the edge of the main scanning start side of the color standard plate and the original, and the scanner head scanning the color standard plate or the original for one scan A latch circuit for holding, for one main scanning period, image data obtained by main-scanning the color chart plate prior to main-scanning the color standard plate or the original when performing main scanning of a line segment; A plurality of look-up tables in which performance fluctuation correction data for correcting fluctuations in image data due to performance fluctuations of the scanner head for each main scan are written, and stored in the latch circuit. A specific look-up table is selected using the image data of the color chart board as a selected address, and the photoelectric conversion means in the selected look-up table is used. A performance variation correction circuit for reading and outputting the performance variation correction data of the image data from an address designated by the color standard plate or the original image data; and A color correction circuit for performing color correction on the performance variation correction data of the image data of the document is provided.

According to a third aspect of the present invention, in the color scanner according to the first or second aspect, the performance variation correction data written in each of the look-up tables is stored in an environment where a steady operation is possible. The image data obtained when the color chart board is scanned is “N”, the data of the selected address associated with the lookup table is “X”, and the address data in the lookup table is “Y”. Then, the characteristic is the performance variation correction data “Z” calculated according to the following equation. Z = (N / X) * Y

[0055]

According to the first aspect of the invention, when the scanner head performs the main scanning of the original for one scanning line, the color chart board is main-scanned before the main scanning of the original, and the color conversion is performed by the photoelectric conversion means. Image data is obtained. Then, the obtained image data of the color chart board is held in the latch circuit for one main scanning period. Subsequently, the original is main-scanned to obtain image data, which is sent to the performance fluctuation correction circuit. Then, a specific lookup table is selected by the performance fluctuation correction circuit using the image data of the color chart board held in the latch circuit as a selection address. Then, the performance fluctuation correction data of the image data is read out and output from the address specified by the image data of the original in the selected look-up table. In this way, the performance fluctuation that occurs every main scanning for one scanning line due to the performance fluctuation of the scanner head is accurately corrected.

In the invention according to the second aspect, the color standard plate is main-scanned by the scanner head before sub-scanning the original. At that time, first, the color chart board is scanned, and color image data is obtained by the photoelectric conversion means. Then, the obtained image data of the color chart board is held in the latch circuit for one main scanning period. Subsequently, the color standard plate is main-scanned to obtain image data, which is sent to the performance fluctuation correction circuit. Then, a specific lookup table is selected by the performance fluctuation correction circuit using the image data of the color chart board held in the latch circuit as a selection address. Then, the performance variation correction data of the image data of the color standard plate is read and output from the address specified by the image data of the color standard plate in the selected look-up table.

Further, when the original is main-scanned by one scanning line by the scanner head, the color chart is first scanned to obtain image data of the color chart, and then the document is scanned. The image data of the document is obtained. Then, in the same manner as in the case of the color standard plate, the performance variation correction circuit performs the performance variation correction based on the image data of the color chart plate, and outputs the performance variation correction data of the image data of the document. You.

Then, the color correction circuit color-corrects the performance variation correction data of the image data of the original based on the performance variation correction data of the image data of the color standard plate.

In this manner, the performance data of the color standard plate and the image data of the document used when performing color correction on the image data of the document are corrected in one main scanning cycle. As a result, performance fluctuations that occur during document scanning are accurately corrected.

According to the third aspect of the present invention, in each of the look-up tables, image data obtained when the color chart board is scanned in an environment where a steady operation is possible is set to "N", When the data of the selected address associated with the lookup table is “X” and the address data in the lookup table is “Y”, calculation is performed according to the formula “Z = (N / X) * Y”. The performance variation correction data “Z” to be performed is written. Therefore, the performance variation correction circuit sets the image data of the color chart board to the selected address data “X” and converts the image data of the color standard board or the original to the address data “Y”.
By obtaining the performance variation correction data “Z” from the look-up table, the color standard plate obtained when the color scanner is used in an environment where steady operation is possible regardless of the environment. Alternatively, image data similar to image data of a document is obtained.

[0061]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a block diagram of the color scanner of the present embodiment, and FIG. 2 is a conceptual diagram of the color scanner. As shown in FIG. 2, the present color scanner has a configuration in which a performance variation correction circuit 50 is added to the conventional color scanner as shown in FIG. Then, when generating the RGB image signal, the performance fluctuation correction circuit 50
The performance fluctuation of the image data for one scanning line is corrected based on the grasped performance fluctuation amount for each main scanning for one scanning line.

Here, the performance variation correction performed by the performance variation correction circuit 50 refers to a case where the above-described color correction mainly corrects a long-to-medium-term performance variation of an optical system based on a change in environmental conditions. This refers to correcting short-term performance fluctuations caused by performance fluctuations of the optical system and mechanical driving condition fluctuations.

Hereinafter, the present color scanner will be described in more detail with reference to FIG. The color scanner includes a document table 51 on which a document 54 is placed, an optical system 52 having a light source 55 and an image sensor 56 and performing sub-scanning movement in parallel with the document table 51 to scan the document 54 and the like. An electric circuit system 53 for processing an electric signal obtained by the system 52 to obtain an image signal composed of RGB image data.

In the vicinity of one end of the document 54 on the document table 51, a white reference plate 57 having a white plate scanned by the optical system 52 before the document 54 is scanned,
Similarly, a color standard plate 58 having at least an RGB reference color chart which is scanned before the original 54 is scanned is installed. Further, in the vicinity of one side of the document 54 on the document table 51, a color standard plate 58 or a color chart plate 5 having a reference color chart scanned before the main scan of the document 54 is provided for each sub-scan.
9 is provided in the sub-scanning direction of the optical system 52. In FIG. 1, the positional relationship among the color chart plate 59, the color standard plate 58, and the document 54 is schematically represented.

The electric circuit system 53 includes an AD converter 60 for quantizing an output signal from the optical system 52 into n bits.
A RAM 61 for storing image data obtained by the AD converter 60 when the white reference plate 57 is scanned, and a white balance circuit 6 for obtaining a white balance of the image data obtained by the AD converter 60 when scanning the original.
2, a corrector 63 for removing shading distortion in the image signal from the white balance circuit 62, and a corrector 6
3, a gamma corrector 64 for correcting the gamma characteristic of the image signal, a performance variation correction circuit 50, a color correction circuit 65, and a performance variation correction circuit 50 and a color correction circuit 65 based on a basic clock. It comprises a timing control circuit 66 for controlling operation timing and a CPU 67 for controlling the color correction circuit 65 to calculate a color correction coefficient.

The performance variation correction circuit 50 latches image data obtained when the color chart plate 59 is scanned and holds the latched image data for one main scanning period. And a correction circuit 72 that corrects the performance fluctuation of the obtained image data based on the image data held in the latch circuit 71.

The color correction circuit 65 has the same configuration as the color correction circuit 19 in FIG. That is, latch circuits 73, 74, and 75 for latching image data from the performance variation correction circuit 50 for each of RGB, a RAM 76 for storing color correction coefficients calculated by the CPU 67, and a RAM 7
A three-state buffer circuit 77 for writing a signal to 6
And latch circuits 78, 79, 80 for latching the color correction coefficients from the RAM 76, and n-bit image data and latch circuits 78, 7 latched by the latch circuits 73, 74, 75.
Multiplier 8 for multiplying 9,80 by the latched color correction coefficient
1, 82, 83, an adder 84 for adding the output data of the multipliers 81, 82, 83, and latch circuits 85, 86, 87 for latching the output data of the adder 84. From 86 and 87, an image signal consisting of corrected RGB image data is output.

FIG. 3 is an external view of the document table 51 as viewed from above, and shows an example of the arrangement of an optical system 52, a document 54, a white reference plate 57, a color standard plate 58, and a color chart plate 59. is there.
The document table 51 is installed in a housing 90. Then, an edge 54 of the document 54 on the document table 51 on the sub-scanning start side.
In the vicinity of “a”, a white reference plate 57 and a color standard plate 58 are arranged side by side in the main scanning direction of the optical system 52. A color chart plate 59 is arranged on the document table 51 near the color standard plate 58 and the side edge 54b on the main scanning start side of the document 54 so as to extend in the sub-scanning direction of the optical system 52.

The above-configured color scanner operates as follows. FIG. 4 and FIG. 5 show a flowchart of an original reading processing operation executed by the color scanner. Hereinafter, the document reading processing operation will be described in detail with reference to FIGS. 1, 3, 4, and 5. The original reading processing operation by this color scanner is shown in FIGS.
As shown by the dotted line in FIG. 4, white balance adjustment, performance variation correction at the time of calculating color correction coefficients, color correction coefficient calculation,
It consists of five processes: correction of performance fluctuation at the time of reading the original, and reading of the original for one scanning line.

When the image reading processing operation starts,
The process "white balance adjustment" is started. This white balance adjustment is performed in exactly the same manner as the white balance adjustment in the color image processing apparatus shown in FIG. Immediately after the optical system 52 starts sub-scanning in step S1, the white reference plate 5 at the scanning line position A in FIG.
7 is main-scanned. In step S2, the image data relating to the white reference plate 57 from the AD converter 60 is stored in the RAM 6
1 is stored. In step S3, when the optical system 52 is moved in the sub-scanning direction toward the color standard plate 58, the RAM 6
On the basis of the image data stored in 1, the white balance circuit 62 adjusts the gain of the circuit so that the RGB image data are all equal. As a result, in the subsequent scanning of the white reference plate 58 and the original 54, white balance is obtained when the obtained image data passes through the white balance circuit 62. Note that the relationship between the image data and the degree of adjustment of the circuit gain is determined in advance.

Subsequently, the above-described process "correction of performance fluctuation at the time of calculating color correction coefficients" is started. In step S4, the optical system 5
2 starts main scanning when it reaches the scanning line position B in FIG. At this time, as shown in FIG. 3, the color chart plate 59 is arranged along the edge of the color standard board 58 on the main scanning start side, so that the color chart board 59 is scanned before the color standard board 58 scans. Is scanned. In step S5, the white balance circuit 62
The image data relating to the color chart plate 59 from
3 to remove shading distortion and the gamma corrector 64
Correction of the gamma characteristic is performed. In step S6,
The image data of the color chart board 59 from the gamma corrector 64 is stored in the latch circuit 71 of the performance variation correction circuit 50. In step S7, based on the image data of the color chart board 59 stored in the latch circuit 71, the correction circuit 72
Is selected from a plurality of look-up tables provided in. The look-up table will be described later in detail.

Subsequently, the above-mentioned process “calculation of color correction coefficient”
to go into. In step S8, the main scanning is further continued at the scanning line position B in FIG.
8 are scanned. In step S9, removal of shading distortion by the corrector 63 and correction of the gamma characteristic by the gamma corrector 64 are performed on the image data of the color standard plate 58 from the white balance circuit 62. In step S10, the color standard plate 58 from the gamma corrector 64
Image data according to the correction circuit 7 of the performance variation correction circuit 50
2 and the performance variation is corrected using the look-up table selected in step S7 as described in detail later. In step S11, based on the image data of the color standard plate 58 for one scanning line, the performance of which has been corrected by the performance
7, a color correction coefficient is calculated. Then, the calculated color correction coefficient is stored in the RAM 76.

That is, in this embodiment, every time the color standard plate 58 is scanned to obtain the image data for calculating the color correction coefficient, the color standard plate 58 is scanned based on the image data obtained. The performance variation of the image data for calculating the color correction coefficient is corrected.

Subsequently, the process "correction of performance fluctuation at the time of reading a document" is started. In step S12, the optical system 5
2 starts the main scanning after reaching the scanning line position C in FIG. At this time, as shown in FIG. 3, since the color chart plate 59 is arranged along the side edge of the original 54 on the main scanning start side, the color chart plate 59 is scanned before scanning the document 24. . In step S13, the corrector 63 corrects the image data of the color patch board 59 from the white balance circuit 62.
, And the gamma corrector 64 corrects the gamma characteristic. In step S14, the contents of the latch circuit 71 of the performance variation correction circuit 50 are updated with the image data on the color chart board 59 from the gamma corrector 64. In step S15, one look-up table is selected from the plurality of look-up tables based on the image data of the color chart board 59 stored in the latch circuit 71 in step S14.

Subsequently, the above-described process "reading of an original for one scanning line" is started. In step S16, the main scanning is further continued at the scanning line position C in FIG. 3 by the optical system 52, and the original 54 is scanned by one scanning line. In step S17, removal of shading distortion by the corrector 63 and correction of the gamma characteristic by the gamma corrector 64 are performed on the image data of the document 54 from the white balance circuit 62. In step S18, the image data of the document 54 from the gamma corrector 64 is sent to the correction circuit 72,
The performance fluctuation correction is performed using the lookup table selected in step S15. Step S19
The image data of the original 54 corresponding to one scanning line, the performance of which has been corrected by the performance fluctuation correction circuit 50, is stored in the RAM 76.
Is color-corrected by the color correction circuit 65 using the color correction coefficient stored in.

That is, in this embodiment, the original 5
Each time one scan line of (4) is scanned to obtain image data to be subjected to color correction, the performance of the image data to be subjected to color correction is determined based on the image data obtained by scanning the color chart board 59. The fluctuation is corrected.

In step S20, it is determined whether or not to scan the next scanning line on the document 54. As a result, if scanning is to be performed, the process proceeds to step S21; otherwise, the image reading processing operation is terminated. In step S21, the optical system 52 is translated by one scanning line of the
Sub-scanning for the scanning lines is performed. Then, step S
Returning to 12, the processing shifts to the performance fluctuation correction at the time of reading the document relating to the next scanning line segment of the document 54. Thus, the above steps S21 and S12 to S20 are repeated to copy the original 5
4 are scanned. If it is determined in step S20 that the next scanning line is not to be scanned, the image reading processing operation is terminated.

As described above, in the present color scanner, after the white balance is adjusted, the color chart plate 59 is scanned each time the sub-scan is performed once before the color standard plate 58 and the original 54 are main-scanned. And the performance variation correction circuit 50
From now on, the amount of performance variation for one main scanning line is grasped in advance. The performance variation correction circuit 50 corrects the performance variation of the image data obtained by scanning the one scanning line based on the grasped performance variation amount of the one scanning line.

That is, in the case of the color image processing apparatus shown in FIG. 13, the performance variation correction is performed every time one image is read, whereas in the present color scanner, every time one scan line of image is read. The performance fluctuation correction is performed. At this time, the image reading for one scanning line is performed as follows.
It does not matter whether the image is read from the color standard plate 58 or the image from the document 54. The color chart board 5
Numeral 9 is provided on the same surface as the color standard plate 58 and the document 54. Therefore, according to the present embodiment, it is possible to reliably correct performance fluctuations caused by mechanical driving condition fluctuations for each sub-scan after white balance adjustment.

Here, as can be seen from FIGS. 4 and 5, the image obtained by one main scan depends on whether the optical system 52 is at the scanning line position B or the scanning line position C in FIG. Processing for data is different. That is, when the optical system 52 is at the scanning line position B in FIG. 3, it is necessary to calculate a color correction coefficient. On the other hand, when it is located at the position of the original 54 such as the scanning line position C in FIG. 3, it is necessary to perform color correction on the image data of the original 54 using the color correction coefficient. Therefore, it is necessary to know whether the current position of the optical system 52 is the position of the color standard plate 58 or the position of the document 54.

As a method of detecting the current position of the optical system 52, a method of mechanically detecting the position of the optical system 52 by providing a switch or a method of constantly monitoring the control state of the drive motor of the optical system 52 by the CPU 67. And so on.

Next, the calculation of the color correction coefficient executed in step S11 and the color correction executed in step S19 of the original reading processing operation shown in FIGS. 4 and 5 will be described. The calculation method and the color correction method of the color correction coefficient executed in the present embodiment are basically the same as those in FIG.
The method is exactly the same as the color correction coefficient calculation method and the color correction method in the color image processing apparatus shown in FIG. However, in this embodiment, the image data sent to the CPU 67 and the color correction circuit 65 is subjected to white balance, shading distortion is removed, and the gamma characteristic is corrected.
The image data has been subjected to the performance fluctuation correction described later in detail by the performance fluctuation correction circuit 50.

The calculation of the color correction coefficient by the CPU 67 is performed as follows. Now, the image data obtained by scanning the red color sample among the samples of the color standard plate 58 is white-balanced, shading distortion is removed, and the gamma characteristic is corrected. 50
It is assumed that the image data R2r, G2r, and B2r are obtained by performing the performance variation correction for each scanning line. Here, the appropriate image data obtained from this red sample is R3r, G
3r, B3r, the red correction coefficient is given by the above equation
According to (2), it is obtained as a matrix coefficient composed of Mr11 to Mr33.

In the same manner, all the color samples constituting the color standard plate 58 are scanned to obtain respective matrix coefficients. The obtained matrix coefficients for each color are averaged to obtain the color correction coefficients M11 to M33, which are stored in the RAM 76 via the three-state buffer circuit 77.

On the other hand, the image data obtained by scanning one scanning line of the document 54 is white-balanced, shading distortion is removed, and the gamma characteristic is corrected. Image data R1, G1, B1 obtained by performing performance variation correction for each scanning line
Are sequentially latched by the latch circuits 73, 74, 75 for each color at the timing shown in FIG. Each of the image data R latched by the latch circuits 73, 74, 75
1, G1, B1 and the color correction coefficient M1 stored in the RAM 76
1 to M33, the corrected image data R0, G0,
B0 is obtained by the above equation (3).

The above-described color correction is performed by the color correction circuit 65 in exactly the same manner as in the case of the color image processing apparatus shown in FIG. Briefly, FIG.
4, the correction coefficient M1x read from the RAM 76 and latched by the latch circuits 78, 79, 80.
Each of (x = 1 to 3) is multiplied by each of the image data R1, G1, and B1 latched by the latch circuits 73, 74, and 75 by the multipliers 81, 82, and 83, respectively. Is converted by the adder 84 to obtain an operation value M11 * R1 + M12 * G1 + M13 * B1, and the result is latched by the latch circuit 85 as corrected image data R0. In the same manner, the operation value M21 * R1 + M22 * G1 + M23 * B1 M31 * R1 + M32 * G1 + M33 * B1 is obtained, and latched by the latch circuits 86 and 87 as corrected image data G0 and B0, respectively. The corrected image data R0, G0, B0 obtained in this way are shown in FIG.
(g) to (i) are output at the timings shown in FIG.

Next, the performance variation correction by the performance variation correction circuit 50, which is a feature of the present invention, will be described with reference to the timing chart shown in FIG. First, in one main scanning period shown in FIG. 6A, as shown in FIG. 6B, the optical system 52 scans the color chart plate 59 prior to the main scanning of the color standard plate 58 or the original 54. The image data (RGB ₀ ) obtained at this time is subjected to corrections such as shading correction and gamma correction, and the latch circuit 71 of the performance fluctuation correction circuit 50
Is latched and stored. The image data (RGB ₀ ′) thus latched by the latch circuit 71 is held during the main scanning period of the scanning line. Needless to say, the image data (RGB ₀ ′) is updated every sub-scan.

The correction circuit 72 of the performance fluctuation correction circuit 50
, In the performance fluctuation detection period shown in FIG. 6 (c), 'sequentially read out, the image data (RGB ₀ image data latched in the latch circuit 71 (RGB _0)' according to the scanning line on the basis of a) Understand the performance fluctuation. Then, FIG. 6 (c)
6B, shading correction and gamma correction are performed on the image data (RGB ₁ ) obtained when the optical system 52 scans the color standard plate 58 or the original 54, as shown in FIG. The performance fluctuation of the image data (RGB ₁ ′) obtained by performing the correction such as the correction is removed (that is, the performance fluctuation is corrected). Hereinafter, the image data (RGB ₀ ′) obtained when the color chart plate 59 is scanned is referred to as correction data, and the image data (RGB ₁ ′) obtained when the color standard plate 58 and the original 54 are scanned is covered. This is called correction data.

Here, in the present embodiment, the above-mentioned data to be corrected is subjected to performance fluctuation correction for each pixel composed of image data of which one set is RGB. Therefore, the correction circuit 72 is required to operate at high speed. Therefore, the correction circuit 72 is stored in the ROM
(Read-only memory), and stores m lookup tables, and realizes high-speed performance fluctuation correction by using the lookup tables.

FIG. 7 schematically shows the structure of the correction circuit (ROM) 72. Each of the data to be corrected and the correction data is an n-bit signal.
, While the data to be corrected is input to a lower bit address terminal 92.
Therefore, for example, if each of the correction data and the data to be corrected is 8 bits, the number of addresses of the correction circuit 27 needs to be 2 ^{(8 + 8)} (= 65536) or more. And
Each address requires 8-bit depth because 8-bit image data obtained by correcting performance variation of 8-bit data to be corrected is written. That is, the ROM constituting the correction circuit 27 requires a capacity of 512 kbits or more.

That is, as described above, the ROM in which n-bit performance variation correction data is written in each of 2 ^{(n + n)} or more addresses is stored in the correction circuit 27 for each of the n-bit upper bit addresses. It is equipped with a plurality of lookup tables divided into individual lookup tables. Then, one look-up table is selected from the m look-up tables, using the correction data input to the upper bit address terminal 91 as the selection address. Then, the address of the selected look-up table is specified by the data to be corrected input to the lower bit address terminal 92, and the performance variation correction data written at that address is output from the output terminal 93. is there.

In order to write the performance variation correction data to each address in the lookup table, image data obtained by scanning the color chart board 59 while the color scanner is operating stably is necessary. is there. Such image data may be obtained by inserting the present color scanner in an environmental test apparatus or the like in advance at the time of development, aging so that the present color scanner operates sufficiently stably, and then scanning the color chart plate. Hereinafter, the image data thus obtained is referred to as “image data N”.

The image data N is created by scanning the color chart plate 59 when the present color scanner is operating ideally. Therefore, when the user actually uses the color scanner, differences between the conditions of the environment where the color scanner is placed and the conditions in the environmental test apparatus, and the difference between immediately after the start of scanning and immediately before the end of scanning. Correction data obtained for each main scan due to differences in temperature conditions due to heat generated by the color scanner itself, mechanical variations, etc.
(That is, image data when scanning the color chart board in the user environment)
Is different from the image data N. Therefore, if the value of the correction data matches the value of the image data N in any environment, no matter what environment the color scanner is used in, the environment test apparatus is always used. The same performance as when used can be exhibited. The purpose of the lookup table is to remove the difference between the correction data and the image data N as described above.

Therefore, the look-up table having the above-mentioned correction data as the upper address contains the performance fluctuation correction data such that the image data of all other values are converted in accordance with the rule of making the correction data equal to the image data N. Is written. By doing so, from the address of the look-up table having the obtained corrected data (that is, image data when scanning the color standard plate in the user environment or when scanning the original) as the lower address, the correction data is converted into the image data. It is possible to read out the image data in which the data to be corrected has been subjected to the performance fluctuation correction in accordance with the rule to be equal to N.

The above look-up table is created by the following procedure. (1) Put this color scanner in the environmental test equipment, etc., and set the temperature, humidity, etc. in the environmental test equipment according to the standard specifications for product shipment. (2) When the color scanner adjusts to the environment in the environmental test equipment and stabilizes, it scans the color chart plate, obtains white balance of the obtained image data, removes shading distortion, and corrects gamma characteristics. Obtain data N. (3) Each address represented by n bits (lower bit address) “Y = 0 to 2” in a lookup table in which the value “X” of n-bit correction data is an upper bit address
Write “Z” obtained by the following equation (4) into each of “ ⁿ ”. Z = (N / X) * Y (4) (4) Set the value of “X” in the range of 0 to 2 ⁿ . Change procedure
Repeat (3) to create all lookup tables.

In the above procedure, as a rule for making the correction data X equal to the image data N, “correction data X
And multiplying by (N / X) times the image data N ”. However, besides the above, "{(N /
X) + h} times (h is a constant). The point is that under the conditions where the color scanner is actually used, the value of the correction data X is formulated using the image data N as a parameter, and the correction is performed by multiplying the correction target data Y by the reciprocal. The rule may be such that the data X is equal to the image data N. For example, what kind of value the correction data X can be obtained by collecting correction data under many conditions where the color scanner is actually used and performing regression analysis or the like with the image data N Can be formulated using the image data N as a parameter. Of course, the above constant h can be determined by such a method.

The look-up table selected in step S7 in the original reading processing operation shown in FIGS. 4 and 5 from the m look-up tables thus prepared and mounted on the correction circuit 72 in the performance fluctuation correction circuit 50. The table is used in the above step S10 at the time of the process "color correction coefficient calculation". Further, the lookup table selected in step S15 is used in step S18 in the process of "document reading".

FIG. 8 is a diagram showing an example of the shape of the color chart board 59. As shown in FIG. The color chart plate 59 in the present embodiment has a reference color chart of “sub-scanning distance × several dots” formed of white paper or resin and is on the same surface as the document 54 mounting surface on the document table 51. The original 54 is arranged in parallel with one side of the original 54 in the sub-scanning direction on the main scanning start side.

As described above, the color chart board 59 has a width of several dots. This width is about 1 mm when the reading resolution is 100 dots / inch. Therefore, when the color chart plate 59 is placed on the document table 51, the reading range of the document 54 is reduced by about 1 mm. However, in general, the range that can be read by the scanner head alone is set slightly larger than the maximum readable document size described in the product specification. For this reason, an ordinary color scanner can read an area slightly larger than the maximum original size described in the specification. That is, the scanner head has some margin for the required read document size. Therefore, by utilizing this margin, the color chart board is set outside the area where the original of the maximum original size described in the specification is placed and within the range that can be read by the scanner head alone. 59 is installed.

In this way, a conventionally used scanner head can be used as it is without changing the design of the scanner head for the present color scanner. The white reference plate 57 and the color standard plate 5
8 and the color chart board 59 are scanned from below by the optical system 52. Therefore, it is possible to cover the upper side with a suitable blind plate. By doing so, the white reference plate 5
7. The color standard board 58 and the color chart board 59 do not touch the eyes of the user, so that the user does not feel uncomfortable.

As described above, in the present embodiment, the color chart plate 5 is extended in the sub-scanning direction along the main scanning start side edge of the color reference plate 58 and the document 54 on the document table 51.
9 is arranged. The gamma corrector 64 and the color correction circuit 6
5, a performance variation correction circuit 50 is provided. And
Each time the optical system 52 is main-scanned, the performance variation correction circuit 50 continuously scans the color chart plate 59 prior to scanning the color reference plate 58 or the document 54 based on the correction data X obtained. The data to be corrected Y obtained by scanning the color reference plate 58 or the document 54 is subjected to performance fluctuation correction. Therefore, based on the image data obtained by scanning the color reference plate 58, when correcting the color of the image data obtained by scanning the document 54, the image data relating to the color reference plate 58 is also stored in the document 54. Such image data also
The performance fluctuation is corrected for each scanning line.

As a result, according to the present embodiment, the second pattern in the long-term performance fluctuation or the medium-term performance fluctuation is removed by correction by the color correction circuit 65. Further, the first pattern in the medium-term performance fluctuation and the short-term performance fluctuation are removed by correction by the performance fluctuation correction circuit 50.

At this time, as described above, the color chart plate 59
The color standard plate 58 is provided independently of the optical system 52.
4 is arranged on the same plane as the mounting surface. Therefore, it is possible to reliably correct performance fluctuations caused by a change in the positional relationship between the document 54 and the optical system 52 due to mechanical backlash. Further, by setting the width of the white voting board 59 to about several dots, the white voting board 59 can be set on the document table 51 at a margin for reading by the scanner head. Therefore, the reading range of the document does not decrease due to the placement of the white vote board 59. In addition, the conventional scanner head can be used as it is, and a dedicated CCD
(Charge-coupled device) can be prevented from increasing in cost.

Further, the performance fluctuation correction circuit 50 has a correction circuit 72. The correction circuit 72 uses image data (correction data) X obtained when the color chart board 59 is scanned as an upper bit address. On the other hand, image data (corrected data) obtained when the color reference plate 58 or the original 54 is scanned.
The performance variation correction data Z of the data to be corrected Y is written to each address having Y as a lower bit address, and a plurality of lookup tables divided for each upper bit address are mounted.

Then, based on the correction data X, one lookup table is selected from a plurality of lookup tables mounted on the correction circuit 72. Thereafter, based on the subsequently obtained corrected data Y, the performance variation correction data Z written at the address of the corrected data Y in the selected look-up table is read and output. Therefore, the performance variation correction circuit 50 can perform the performance variation correction of the data Y to be corrected at high speed in real time. Further, the performance variation correction circuit can be configured at a lower cost as compared with the case where the performance variation correction of the corrected data Y is performed by the arithmetic processing by the CPU.

In the above embodiment, the color chart 5
The reference color chart of No. 9 is “white”. However, the color is not necessarily limited to “white” and other colors may be used. However, in this case, a plurality of colors including three colors of RGB are desirable so that correction data can be obtained independently for RGB phases. For example, in the case of a color chart plate 59 'having an RGB reference color chart, RGB
The color patch board 59 'is formed as shown in FIG. 9 so that the reference color patch is scanned. In that case, a look-up table is also created for each of RGB and mounted on the correction circuit 72 so that the data to be corrected can be subjected to the performance variation correction independently of RGB.

[0107]

As is apparent from the above description, in the color scanner according to the first aspect of the present invention, the scanner head uses one original.
When performing main scanning of scanning lines, a color chart plate to be main-scanned is placed on a document table prior to main scanning of the original, and the performance variation correction circuit causes the scanner head to perform one main scanning of the original. Based on the obtained color chart plate and the image data of the original, the performance variation correction data of the image data of the original is obtained using a look-up table, so that the color scanner performs main scanning for one scanning line. The performance fluctuation can be corrected every time. Therefore, according to the present invention, it is possible to correct the performance fluctuation that occurs each time one scanning line of image is read.

At this time, the color chart board is set on the document table independently of the scanner head, like the document. Therefore, it is possible to correct not only the performance fluctuation due to the performance fluctuation of the optical system mounted on the scanner head but also the performance fluctuation due to the mechanical driving condition fluctuation. Further, since the performance fluctuation correction by the performance fluctuation correction circuit is performed by using the look-up table, it is executed at a very high speed in real time.

In the color scanner according to the second aspect of the present invention, a color standard plate for main scanning is set on a document table before the scanner head sub-scans an original, and the scanner head is mounted on the color standard plate or the color standard plate. When the main scanning of the original is performed for one scanning line, the color standard plate or the color chart plate to be main-scanned before the main scanning of the original is set on the original platen. Based on the color plate image data obtained when the main scanning of the color standard plate or the original by one main scan, the performance variation correction data of the image data of the color standard plate or the original is obtained using a lookup table, The color correction circuit corrects the color of the image data of the document whose performance has been corrected based on the image data of the color standard plate whose performance has been corrected. Also modifying the performance variation occurring after obtaining the image data of the color standard plate, it can be performed more accurately color correction.

Further, in the color scanner according to the third aspect of the present invention, in each lookup table, image data obtained when the color chart board is scanned in an environment in which a steady operation is possible is set to “N”. The data of the selected address associated with the lookup table is “X”, and the address data in the lookup table is “Y”.
Since the performance variation correction data “Z” calculated according to the equation “Z = (N / X) * Y” is written,
When correcting the performance fluctuation by the performance fluctuation correction circuit,
Obtaining performance variation correction data "Z" from the lookup table, with the image data of the color chart board as the selected address data "X" and the image data of the color standard board or original as the address data "Y". Accordingly, no matter what environment the color scanner is used, image data similar to the image data of the color standard plate or the original document obtained when the color scanner is used in an environment capable of steady operation can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a color scanner according to the present invention.

FIG. 2 is a conceptual diagram of the color scanner shown in FIG.

FIG. 3 is a diagram showing an arrangement example of an optical system, a document, a white reference plate, a color standard plate, and a color chart plate in FIG. 1;

FIG. 4 is a flowchart of a document reading process operation.

FIG. 5 is a flowchart of a document reading process operation continued from FIG. 4;

FIG. 6 is a timing chart of performance fluctuation correction by the performance fluctuation correction circuit in FIG. 1;

FIG. 7 is a schematic diagram showing a structure of a correction circuit in FIG. 1;

FIG. 8 is a diagram showing an example of the shape of the color chart plate in FIG. 1;

FIG. 9 is a diagram showing a shape of a color chart plate different from that of FIG. 8;

FIG. 10 is a schematic diagram showing a state of performance fluctuation in a conventional color scanner.

FIG. 11 is a diagram showing a structure near a scanner head in a conventional color scanner.

12 is a diagram illustrating a state of an angle change between the scanner head and a document due to play in a drive system of the scanner head illustrated in FIG. 11;

FIG. 13 is a block diagram of a conventional color image processing apparatus.

14 is a diagram showing operation timings of the color correction circuit in FIG.

FIG. 15 is a schematic diagram showing a state of performance fluctuation remaining after performance fluctuation correction by a conventional image processing apparatus having a performance fluctuation correction function.

[Explanation of symbols]

50: performance fluctuation correction circuit, 51: platen, 5
2: Optical system, 54: Original, 57:
White reference plate, 58 ... Color standard plate, 59 ...
Color chart board, 65 ... Color correction circuit, 67
... CPU, 71,73-75,78-80,85-87 ...
Latch circuit, 72... Correction circuit, 81
83 to multiplier; 84 to adder.

Continuation of the front page (56) References JP-A-3-132254 (JP, A) JP-A-63-148379 (JP, A) JP-A-63-224475 (JP, A) JP-A-63-142960 (JP) JP-A-62-104362 (JP, A) JP-A-62-78962 (JP, A) JP-A-61-252746 (JP, A) JP-A-61-30865 (JP, A) 56-111374 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1/04-1/207

Claims (3)

(57) [Claims] 1. A color scanner for scanning a document placed on a platen by a scanner head to obtain color image data by photoelectric conversion means, wherein a sub-scan is performed along a side edge of the document on a main scanning start side. A color chart board extending on the document table and extending in the direction, and when the scanner head performs main scanning of the document for one scanning line, the color chart board is scanned prior to the main scanning of the document. A latch circuit for holding image data obtained by main scanning for one main scanning period; and a latch circuit associated with the selected address and correcting a change in image data due to the performance fluctuation of the scanner head for each main scan. A plurality of look-up tables in which performance variation correction data is written, and image data of the color chart plate held in the latch circuit as a selection address. A performance variation correction circuit for selecting an up table and reading out and outputting performance variation correction data of the image data from an address designated by the image data of the original from the photoelectric conversion means in the selected look-up table; A color scanner. 2. A color scanner for scanning a document placed on a platen by a scanner head to obtain color image data by photoelectric conversion means, wherein a main scan is performed along an edge of the document on a sub-scanning start side. A color standard plate having a reference color chip of at least red, green and blue, and a color standard plate having at least a reference color chip of red, green, and blue. A color chart plate extending on the platen; and a main scan of the color standard plate or the original when the scanner head performs a main scan of the color standard plate or the original for one scanning line. A latch circuit for holding image data obtained by main-scanning the color chart board in advance for only one main scanning period, and an image data associated with a selected address and caused by a performance variation of the scanner head. A plurality of look-up tables in which performance fluctuation correction data for correcting fluctuations for each main scan are written; and a specific look-up using the image data of the color chart board held in the latch circuit as a selection address. A performance variation correction for selecting a table and reading out and outputting performance variation correction data of the image data from an address designated by the color standard plate or the original image data from the photoelectric conversion means in the selected lookup table. A color scanner, comprising: a circuit; and a color correction circuit that performs color correction on the performance variation correction data of the image data of the document based on the performance variation correction data of the image data of the color standard plate. 3. The color scanner according to claim 1, wherein the performance variation correction data written in each of the look-up tables is used when the color chart board is scanned in an environment in which a steady operation is possible. Assuming that the obtained image data is “N”, the selected address data associated with the lookup table is “X”, and the address data in the lookup table is “Y”, the performance calculated according to the following equation: Fluctuation correction data "Z"
A color scanner, characterized in that: Z = (N / X) * Y