JPH11234528A - Image reader, its method and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color scanner capable of high speed processing with high color reproducibility at low cost. SOLUTION: The reader is provided with an arithmetic section 106 that uses image data (a) of a current input line and image data (n) of one line- preceding read from a memory 104 in the same color as that of the input line to conduct a weight mean arithmetic operation and that outputs the arithmetic result. The reader is also provided with a parameter setting means (CPU 108) that sets a parameter (c) for the arithmetic operation to each reading of each color. The weighting means arithmetic operation is conducted by using the parameter (c) different from each color. Thus, an image without color slurring is obtained through a moving readway.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, an image reading method, and a recording medium, and more particularly, to an image reading apparatus suitable for use in a color scanner that performs color reading by switching the emission color of a light source.

[0002]

2. Description of the Related Art There is a color scanner which performs color reading by switching the emission color of a light source. Such a scanner uses Red, Green, Blue (hereinafter referred to as R,
G and B), and a line-type image sensor is used in the reading unit. The light of each color emitted from the LED illuminates a portion including the reading line on the document, and the reflected light from the document surface enters the sensor IC via the lens array.

[0003] A line-type image sensor constituted by a sensor IC has a photoelectric conversion element such as a photodiode and a capacitor for each pixel, converts incident light into a current, and accumulates the electric charge in the capacitor. The stored charges are sequentially converted into voltages and output. The voltage output is converted into digital data by an AD converter, subjected to various image processing, and output as a scanner output.

The operation of color reading is as follows. That is, first, the red LED is turned on to read one line in the main scanning to obtain the red component of the color image. Then, the green LED is turned on to obtain the green component.
Obtain n components. Finally, turn on the blue LED and
lue component is obtained. When reading of three colors for one line is completed, the document is conveyed in the sub-scanning direction, and reading of the next one line is performed in the same manner. This is repeated to read one page of color image.

In such a conventional example, for example, one line 1
If a time of 5 ms is required for reading a color, a time obtained by adding 15 ms to the original scanning time in the sub-scanning direction is required for reading one line. If it takes 5 ms to transport the original, the time required to read one line is 2
0 ms. Hereinafter, such reading control is referred to as still reading.

On the other hand, in a monochrome reading system such as a facsimile, the reading time is shortened by carrying the document in the sub-scanning direction while reading the image.
For example, while reading an original for one line in a time of 5 ms, the original is transported to the next line. As a result, reading can be performed continuously in units of 5 ms. Hereinafter, such reading control is referred to as moving reading.

[0007]

In order to increase the speed of color reading, a method of applying moving reading of a monochrome system to color reading can be considered. In this case, the original is conveyed in the sub-scanning direction for one line while reading three colors for one line of the image. For example, one line of original is conveyed while reading one line for 15 ms. At this time, the transport time is one-third of the static reading time. Therefore, the transport control circuit can be greatly simplified, an inexpensive reading system can be realized, and the original reading and transport are performed simultaneously. , High-speed reading can be realized.

However, in this method, since the position on the document from which each color is read is shifted by 1/3 line, there is a problem that color bleeding occurs at a black horizontal edge portion or the like. is there. Therefore, conventionally, such a color reading system can only employ still reading, and there is a problem that the reading system becomes slow and expensive.

Further, in the above conventional example, since the focal depth for each color is different due to the chromatic aberration of the lens array, the resolution differs for each color, and the read data, which should be a black fine line, is no longer black or black. There was a problem that the edge was colored. On the other hand, if a lens having no chromatic aberration is used, there is a problem that the lens becomes large and the cost increases, and the apparatus becomes expensive and large.

The present invention has been made to solve such a problem, and has as its object to provide an image reading apparatus which is inexpensive, has high color reproducibility, and can perform high-speed processing. In particular, with respect to the color reproducibility, it is also an object to use an inexpensive lens having chromatic aberration and to improve the color reproducibility of black fine lines and black edges when moving reading is performed.

[0011]

According to the present invention, there is provided an image reading apparatus which obtains color image data by performing a plurality of readings with a line sensor while changing the emission color of a light source. A line memory for sequentially storing at least one line of input image data every time;
A calculating means for calculating using the image data of the input line and the image data of the same color as the input line read from the line memory, and outputting the calculation result; and Parameter setting means for setting each reading.

Here, the calculation may be a weighted average calculation of the image data of the input line and the image data read from the line memory. In this case, the parameter of the calculation may be the weight of the weighted average.

Further, the parameters for the above calculation may be obtained by performing a predetermined calculation on the parameter values used when the previous image data of the same color was output. In this case, the initial values of the parameters of the above calculation may be set to different values for each color. Further, a numerical value proportional to an image reduction ratio or a reciprocal of a line thinning ratio may be used in the predetermined calculation performed on the parameter value used at the time of the previous image data output.

Further, a means may be provided for changing the lighting time duty of the light source within one cycle of the line synchronization for each color to balance the output of each color. In this case, the initial value of the parameter may be determined for each color by using the lighting time duty of each color for calculation.

Further, two registers for storing the parameters of the operation may be provided, and the parameters set by the parameter setting means may be derived to the operation means via the two-stage registers.

Another feature of the present invention is that in an image reading apparatus which obtains color image data by reading with an image sensor, the output of the image sensor is AD-converted, and the obtained image data is converted. Computing means for performing an edge enhancement operation with different parameters for each color and outputting the result, and control means for controlling the edge enhancement degree of a color having a low resolution among the colors to increase the edge enhancement degree. .

Here, the parameter may be a coefficient representing the strength of the edge enhancement. Further, two registers for storing the parameters may be provided, and the set parameters may be derived to the arithmetic means via the two registers.

According to the image reading method of the present invention, in the image reading method of obtaining color image data by performing a plurality of readings with a line sensor while changing the emission color of a light source, a parameter used for calculation is set for each reading of each color. Set to
According to the set parameters, a calculation is performed for each reading of each color using the image data of the input line and the image data of the previous line of the same color as the input line, and the calculation result is output. I do.

Here, the calculation may be a weighted average calculation of the image data of the input line and the image data of the previous line of the same color as the input line.

According to another feature of the present invention, in an image reading method for obtaining color image data by reading with an image sensor, the image data obtained by AD-converting the output of the image sensor is used. In addition, an edge emphasis calculation is performed using different parameters for each color so as to increase the degree of edge emphasis of a low-resolution color, and the color is output.

A computer-readable recording medium according to the present invention is an image reading apparatus that obtains color image data by reading a plurality of times with a line sensor while changing the emission color of a light source. Calculating means for performing a weighted average calculation using the input line and the image data of the same color one line before, and outputting the calculation result;
And a program for causing a computer to function as parameter setting means for setting the parameters of the calculation in the calculation means for each reading of each color.

Another feature of the present invention is that in an image reading apparatus which obtains color image data by reading with an image sensor, the output of the image sensor is AD-converted, and the obtained image data is converted. A program for causing a computer to function as control means for performing edge enhancement calculation with different parameters for each color and outputting the result, and control means for controlling the edge enhancement degree of a color having a low resolution among the above-mentioned colors. It is recorded.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram that best illustrates the features of an image reading apparatus according to the present invention, and illustrates the configuration of a color scanner as an example. In FIG. 1, reference numeral 108 denotes a CPU for controlling the entire system;
A RAM 110 used as a work area and an image data storage area is a ROM for storing a control program of the CPU 108. Reference numeral 111 denotes a DMA controller which performs DMA (Direct Memory Access) transfer between the reading unit 119 and the RAM 109.

The above-mentioned CPU 108, RAM 109, R
The OM 110, the DMA controller 111, and the reading unit 119 are mutually connected via a system bus 117. The CPU 108 accesses each block connected to the system bus 117 according to a control program in the ROM 110.

Reference numeral 101 denotes a line sensor unit.
For example, it is configured by integrating an image sensor such as a contact image sensor or a CCD and a light source such as an LED. This sensor 101 is a color register 1
One of the three color (R, G, B) LEDs is turned on in accordance with the light source color selection signal COLOR output from 15. When the sensor 101 receives the line synchronization signal SYNC output from the timing control unit 114, the sensor 101 initializes an internal pixel counter and starts reading a document.

An AD converter 102 converts the analog output voltage from the sensor 101 into digital multi-valued image data. Reference numeral 103 denotes a correction circuit, which performs a digital operation or a conversion by referring to a table on the digital output from the AD converter 102 to obtain a sensor 101.
Data a in which the sensitivity variation of the light source, the non-uniformity of the light amount of the light source, and the non-linearity with respect to the incident light amount of the sensor 101 are corrected.
Is output.

A line memory 104 stores the image data of the previous line, and has a capacity of one line for each of R, G, and B colors. Reference numeral 105 denotes a memory control unit which reads out pixel data b of the previous line of the same color as the current input line from the line memory 104 for each pixel during the image processing, and outputs the read data to the address on the line memory 104. Is controlled to write the pixel data a of the current line supplied from. Such a memory control unit 105
, The line memory 104 may have one line for each color, but may have a plurality of lines.

Numeral 106 denotes an arithmetic unit, which stores the pixel data a of the current line input from the correction circuit 103 and the memory control unit 1
The pixel data “b” of the previous line input from “05” is calculated using the parameter “c” input from the parameter register 113, and the calculation result “d” is output. The content of the operation is d = (b × (c−1)) + (a × c) (where c ≦ 1). That is, the calculation result d is a weighted average of the pixel data a of the current line and the pixel data b of the previous line, and the parameter c is a weight for the pixel data a of the current line.

Reference numeral 107 denotes a DMA interface.
The weighted average pixel data d output from the arithmetic unit 106 is input, and the input signal is output to the internal bus 118 according to the timing control of the DMA controller 111. As a result, the weighted average pixel data d output to the internal bus 118
Is written to the RAM 109 via the system bus 117.

The read line synchronizing signal SYNC output from the timing control unit 114 is transmitted to the parameter register 113 and the color register 11 in addition to the sensor 101.
5, also input to the CPU 108. Upon receiving the synchronization signal SYNC, the parameter register 113 latches the contents of the parameter register 112 at the preceding stage. That is, the parameter c is updated in synchronization with the synchronization signal SYNC. Further, the color register 115 stores the synchronization signal S
When the YNC is received, the color register 1 in the preceding stage is received.
16 is latched. That is, the light source color selection signal C
OLOR is updated in synchronization with the synchronization signal SYNC.

Further, the CPU 108 controls the synchronization signal SYNC
Is received, interrupt processing is started, and parameters are written to the parameter register 112 via the system bus 117 and the internal bus 118 in the interrupt routine. Further, information specifying a light source is written in the color register 116 in the interrupt routine. That is, the next synchronization signal S
Parameter c applied from YNC and light source color selection signal CO
LOR can be reserved in each of the registers 112 and 116.

Next, the operation of correcting color misregistration during moving reading will be described with reference to FIG. In FIG. 2, the horizontal direction is the sub-scanning direction, and the R row represents the reading position by the Red light source. G line is Green light source, B line is Blue
This indicates the reading position by the light source. The reading position by each light source actually has a width in the sub-scanning direction, but is illustrated as having no width for explanation.

The reading order is R1, G1, B1, R
2, G2, B2, R3, G3, B3,. Here, since the moving reading is being performed, the original is being conveyed by ラ イ ン line at a time during reading in the order of R, G, and B. As a result, for example, R1, G1, and B1 are shifted by 1/3 line in the sub-scanning direction. If this is processed as it is as a reading result for one line, color misregistration may occur.

For example, when reading a black horizontal edge,
Even during the R reading, a black portion may be read during the B reading even if the edge is not on the edge. In this case, the luminance data of each color becomes R>G> B, and the data that should be gray, where R = G = B, becomes reddish data. That is, color shift occurs at the edge portion. Therefore, in the present embodiment, the color shift is corrected by the following method.

When the logical read position is the broken line portion (R2 portion) in FIG. 2, R2 may be used as read data for Red. In contrast, G
As for the reen, the logical reading position is G1-G2.
between. Therefore, assuming that the distance between G1 and G2 is 1 and the distance between the logical reading position and G1 is c = ２, the calculated value of G1 × (c−1) + G2 × c is the value of Green. Thus, data of the logical reading position can be obtained in a pseudo manner. That is, this corresponds to the case where the pixel data a of the current line in FIG. 1 is G2, the pixel data b of the previous line is G1, and c = 2/3.

Similarly, by setting c = 1/3 for Blue and setting the calculated value of B1.times. (C-1) + B2.times.c to the value of Blue, data of the logical read position can be obtained in a pseudo manner. it can. This corresponds to the case where the pixel data a of the current line in FIG. 1 is B2, the pixel data b of the previous line is B1, and c = 1/3. For Red, R2 was used as the value of the read data.
Corresponds to the case of

As described above, when reading R2, G2, and B2, the values of the parameters are set to c = 1, c = 2/3,
By performing a weighted average calculation process with c = 1/3,
An image without color shift can be obtained by moving reading. That is, by performing reading image processing with a different parameter c for each color, it is possible to obtain an image with no color shift in moving reading.

Next, regarding the setting operation of the parameter c,
This will be described with reference to FIG. The timing control unit 114 of FIG.
Outputs the synchronization signal SYNC, the CPU 108 receives the synchronization signal SYNC and performs an interruption process as shown in the flowchart of FIG. The contents of the interrupt processing are
It is as follows.

First, the color of the light source for the next line is determined in step S1, and the determined color information is written in the color register 116 in step S2. With this, the next synchronizing signal SY
This means that the light source color for reading started from the NC has been reserved. Here, the light source color of the next line is reserved instead of the light source color of the current line whose reading has been started in synchronization with the synchronization signal SYNC, because the interrupt response time is long before the output of the first pixel. This is because there is a case where writing to is not in time.

Next, in step S3, the color of the next output line is determined. If the color of the next output line is R, the process proceeds to step S4, if it is G, the process proceeds to step S5, and if it is B, the process proceeds to step S6. In steps S4, S5, and S6, the value of the parameter c is determined to be 1, 2/3, and 1/3, respectively. Next, in step S7, the determined parameter c is written in the parameter register 112, and this interrupt processing ends.

As described above, in this embodiment, R, G, B
At the time of reading c = 1, 2 /
By performing the processing as 3/3, it is possible to obtain an image with no color shift by moving reading. That is, by performing read image processing with different parameters c for each color, it is possible to realize an inexpensive and high-speed reading system with excellent color reproducibility and greatly simplified control circuit for document conveyance.

(Second Embodiment) The second embodiment is adapted to cope with a case where the original is changed in magnification at the time of reading. Hereinafter, the setting of the parameter c when scaling (reducing) will be described with reference to FIG. Note that the example of FIG. 4 shows a case where the sub-scanning direction is reduced to 3/4 times.

In FIG. 4, the process from the reading of R2 to B2 is the same as that of the first embodiment, but the next reading of R3 does not employ the pixel data d obtained by averaging R3 and R2. That is, control is performed so that DMA transfer is not performed. Next, at the time of reading G3, by reading with c = 1, the value of G3 is output as it is as the value of Green's implicit reading position. Next, when reading B3, reading is performed at c = ２, and when reading R4, reading is performed at c = 1/3. That is, the image data of the second line is obtained in the order of G, B, and R.

Similarly, the image data of the third line is
It is obtained by reading at B = 1, 2/3, and 1/3 at the time of reading B4, R5, and G5 without using the reading data of G4.

Next, the method of determining the parameter c in steps S4, S5, and S6 in FIG. 3 when performing image reduction will be described with reference to FIG. In FIG. 5, read
_Position is a variable that holds the distance from the reading position of the physical previous line to the next logical reading position,
This is a variable independently secured for each of R, G, and B.

First, in step S501, the variable read_posi
Check whether the value of Option is 1 or less. If it is 1 or less, the next logical reading position exists before the next physical reading position, so that a combined output is obtained at the next physical reading. In this case, the process proceeds to step S502. In step S502, a DMA transfer operation from the next synchronization signal SYNC is reserved in the DMA I / F 107. In this case, since the variable read_position is the parameter c itself, the value of the variable read_position is set in the parameter register 112.

Next, in step S503, the variable read_po
The value of sub_distance is added to the value of sition. Above sub
_Distance is the interval between logical reading positions. In the case of image reduction, sub_distance> 1. Next, in step S504, the variable read_po is obtained by subtracting 1 which is the physical reading interval from the value of read_position.
The sition indicates the distance from the next physical reading position to the subsequent logical reading position.

In step S501, the variable read_positi
If the value of on is greater than 1, the next logical reading position is ahead of the next physical reading position, so that a composite output cannot be obtained at the next physical reading. In that case, the process jumps to step S504. In step S504, the variable read_position is subtracted from the read_position value by 1 which is the physical reading interval.
The position indicates the distance from the next physical reading position to the subsequent logical reading position.

For example, the case of R reading in FIG. 4 will be described as follows. Note that the variable read_posi
The initial value of Option is 1, and the value of sub_distance is the reciprocal of the reduction ratio or the line thinning ratio, that is, 1.33.
First, the synchronization signal SYN at the time of reading the pixel B1
In the interrupt processing by C, a parameter c for the output data of R2 is set.

Here, since the value of the variable read_position of R is 1, a DMA reservation is made in step S502, and the value of the variable read_position (= 1) at that time is set in the parameter register 112 to read the pixel of R2. Sometimes reading is performed with the parameter value c = 1. After that, the interrupt processing ends at read_position = 1.33 by the processing of steps S503 and S504.

Next, a parameter c for the output data of R3 is set by interrupt processing by the synchronization signal SYNC when reading the pixel of B2. Here, since the value of the variable read_position of R is 1.33, step S5
02, the processing of S503 is not performed, and R
Is updated to 0.33, and the interrupt processing ends.

Next, in the interrupt processing by the synchronization signal SYNC when reading the pixel B3, the variable read of R is read.
Since the value of _position is 0.33, a DMA reservation is made in step S502, and the value of the variable read_position (= 0.33) at that time is set in the parameter register 112. Reading is performed at c = 0.33. Thereafter, by the processing of steps S503 and S504, read_
Assuming that position = 0.66, the interrupt processing ends.

In the case of G reading, the variable read_posi
The initial value of Option is 1.66, and sub_distance is the reciprocal of the reduction ratio, that is, 1.33, as in R reading. First,
In the interrupt processing by the synchronization signal SYNC of R1, the parameter c for the output data of G1 is set. Here, since the value of the variable read_position of G is 1.66, the processing of steps S502 and S503 is not performed, and the processing of step S502 is not performed.
At 504, the value of the variable read_position of G is updated to 0.66, and the interrupt processing ends.

Next, in the interrupt processing by the synchronization signal SYNC of R2, the value of the variable read_position of G is set to 0.66.
Therefore, a DMA reservation is made in step S502, and the value of the variable read_position (= 0.66) at that time is set in the parameter register 112, so that when G2 is read, reading is performed with the parameter value c = 0.66. To do. Thereafter, by the processing of steps S503 and S504, read_position = 1 is set, and the interruption processing is ended.

Similarly, in the case of B reading, the variable read_po
By setting the initial value of sition to 1.33 and sub_distance to 1.33, which is the reciprocal of the reduction ratio, as in the case of R reading, data at the logical reading position can be obtained.

As described above, the R read variable read_posi
The variable re different for each color, such as an initial value of 1, an initial value of the variable read_position for G reading 1.66, and an initial value of the variable read_position for B reading 1.33.
Using the initial value of ad_position, a variable independently for each color
By performing the read_position calculation and determining the parameter c, it is possible to perform moving reading without color shift even when the image is reduced. Here, the image reduction has been exemplified, but the same can be applied to the magnification of the image enlargement.

(Third Embodiment) In the color reading system, since the luminance of the LED of the light source greatly varies, in the third embodiment, this variation is corrected by adjusting the lighting time. FIG. 6 shows this state. In FIG.
Since the document transport amount in the sub-scanning direction is proportional to the document transport time, the timing on the time axis and the reading position are shown on the horizontal axis.

The line synchronization signal S for each of R, G, and B colors
The light is turned on in synchronization with the YNC, and is turned off after a lighting time independently set for each color elapses. In the example of FIG. 6A, the case where the lighting time is R = 5/6, G = 1/3, and B = 1/2 is shown. When such lighting time control for each color is performed, the reading position of each color is considered to be located at the center of the lighting range, so the reading position is as shown by the upper arrow in FIG. 6B. That is, G is shifted by 0.25 lines with respect to R, and B is shifted by 0.61 lines with respect to R.

That is, the reading position of R, G, B is 1
It does not shift by / 3 lines. Therefore, the initial value of the variable read_position for each color is 1, 1.66,
With 1.33, it is not possible to reliably correct the color misregistration.
Therefore, in such a case, the variables read for R, G, and B are read.
The initial values of _position are 1, 1.25, 1.61, respectively.
By doing so, the color shift can be corrected.

Here, the deviation amount of G from R is (1+ (G lighting time / line synchronization interval) / 2− (R lighting time / line synchronization interval) / 2) × (1/3) = 0.25 Thus, it can be calculated from the lighting time. Therefore,
By calculating and calculating the initial value of the variable read_position of each color from the lighting time of each color, moving reading can be performed without color shift even if lighting time control is performed.

In the present embodiment, a rational number expression such as 1/3 is used. However, the precision is limited in an actual digital arithmetic circuit, so that a rounding process is required. For example, for 7-bit precision, 1 is set to 80H (hexadecimal notation), and 1 /
3 can be expressed by 2AH or the like.

(Fourth Embodiment) FIG. 7 is a diagram showing the characteristics of an image reading apparatus according to a fourth embodiment best.
The configuration of a color scanner is shown as an example. In addition,
In FIG. 7, components denoted by the same reference numerals as those shown in FIG. 1 have the same functions, and therefore, detailed description thereof will be omitted, and only the configuration different from that of the first embodiment will be described. explain.

In FIG. 7, the line memory 704 stores 1
A line buffer for storing the image data before the line and the image data two lines before, and has a capacity of two lines for each of R, G and B colors.

During image processing, the memory control unit 705 reads, from the line memory 704, pixel data of the previous line and the line immediately before the same line in the main scanning direction and the same line as the current line from the line memory 704 for each pixel. The data b and the pixel data e before the line are output. Further, control is performed so that the pixel data a of the current line supplied from the correction circuit 103 is written to the read address of the line pixel before the second line on the line memory 705. Such a memory control unit 70
By the control of 5, the line memory 704 may have two lines for each color, but may have three or more lines.

The arithmetic unit 706 also stores the pixel data a of the current line input from the correction circuit 103 and the memory control unit 7
The pixel data b of the previous line and the pixel data e of the line two lines before are input from the parameter register 113 using the parameter c input from the parameter register 113, and the operation result d is output. The content of the operation is as follows: d = b _n-1 + c × (4 × b _n-1 − (a _n-2 + a _n + e
_n-2 + is a e _n)). This is an operation for performing edge enhancement processing on the pixel data b _n−1 of the previous line.

In the above equation, the suffix represents the pixel position in the main scanning direction as shown in FIG. Where a _n , b _n , e _n
Are the pixel data a of the current line, the pixel data b of the previous line, and the pixel data e of the line two lines before, respectively. b
_n-1 is a delayed one pixel input b _n within the arithmetic unit 706. With such a configuration, a two-dimensional filter is configured to perform edge enhancement processing on the pixel data b _{n−1 of the} previous line. Further, c is a parameter for controlling the strength of edge enhancement. If the value is 0, the pixel data b _n-1 of the previous line is output as it is, and no correction is performed. The greater the value of the parameter c, the greater the amount of edge enhancement.

Next, regarding the setting operation of the parameter c,
This will be described with reference to FIG. The timing control unit 114 of FIG.
Outputs the synchronization signal SYNC, the CPU 108 receives the synchronization signal SYNC and performs an interrupt process as shown in the flowchart of FIG. The contents of the interrupt processing are
It is as follows.

First, the color of the light source for the next line is determined in step S1, and the determined color information is written in the color register 116 in step S2. With this, the next synchronizing signal SY
This means that the light source color for reading started from the NC has been reserved. Next, in step S3, the color of the next output line is determined. If the color of the next output line is R, the process proceeds to step S4, if it is G, the process proceeds to step S5, and if it is B, the process proceeds to step S6. In steps S4, S5, and S6, the value of the parameter c is determined. Here, a method of determining the parameter c will be described with reference to FIG.

FIG. 10 is a diagram showing an example of luminance data of a black and white edge portion. For example, consider the case where the read data of the black edges of R and G is data as shown in FIG.
In this case, R has a higher resolution. Therefore, if the value of the parameter c is set to 0 for R and an appropriate value is set to the parameter c for G only, the edge enhancement is not performed for R, and the result of the edge enhancement processing indicated by the broken line for G is obtained. can get.

That is, by performing edge enhancement with different edge enhancement amounts for R and G, G read data becomes closer to R read data. That is, by controlling the edge enhancement degree of G to be strong, it is possible to improve the resolution of G having a low resolution in a pseudo manner and to approach the resolution of R.

Next, in step S7 in FIG. 9, the determined parameter c is written in the parameter register 112, and the interrupt processing ends. Now the next synchronization signal S
This means that the reading parameter c started from the YNC is reserved. Here, the light source color and the parameter c of the next line are reserved instead of the light source color and the parameter c of the current line whose reading is started in synchronization with the synchronization signal SYNC. Since the light sources of two colors emit light during the synchronization period, the color reproducibility deteriorates, or the update of the parameter c on the register cannot be completed by the time the processing of the first pixel is started. This is because they may not be able to do so.

Conversely, in a system where the interrupt response time is limited to within an allowable range, the color register 115 and the parameter register 113 are directly connected to the internal bus 118, and the color information is stored in the color register 115 in step S2 in FIG. Is set, and in step S7, the parameter register 1
13, the parameter c may be written.

As described above, in this embodiment, R, G,
Performs edge enhancement with different edge enhancement amounts for each color of B,
Furthermore, by increasing the amount of edge enhancement for low-resolution colors, it is possible to approximate the resolution of each color in a pseudo manner,
The color reproducibility of black fine lines and black edges can be improved.
That is, even when an inexpensive lens having chromatic aberration is used, the color reproducibility of the black fine line and the black edge can be improved, and a low-cost reading system with good color reproducibility can be realized.

(Other Embodiments of the Present Invention) In the above embodiment, a color scanner has been described as an example. However, the present invention relates to a plurality of devices (for example, a color scanner, a host computer, an interface device, a reader, a printer, etc.). ) Is applied to a single device (for example,
(A color scanner, a color copying machine, a color facsimile machine).

Further, in order to operate various devices for realizing the functions of the above-described embodiments, an apparatus connected to the various devices or a computer in a system is required to realize the functions of the above-described embodiments. The present invention also includes a software program code supplied and implemented by operating the various devices according to a program stored in a computer (CPU or MPU) of the system or the apparatus.

In this case, the program code of the software implements the functions of the above-described embodiment, and the program code itself and means for supplying the program code to a computer are provided.
For example, a storage medium storing such a program code constitutes the present invention. As a storage medium for storing such a program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
A magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

Further, when the computer executes the supplied program code, not only the functions of the above-described embodiment are realized, but also the OS (operating system) or other operating system running on the computer. Needless to say, even when the functions of the above-described embodiments are realized in cooperation with application software or the like, such program codes are included in the embodiments of the present invention.

Further, after the supplied program code is stored in a memory provided in a function expansion board of a computer or a function expansion unit connected to the computer, the function expansion board or the function expansion unit is specified based on the instruction of the program code. It is needless to say that the present invention also includes a case where the CPU or the like provided in the first embodiment performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0079]

As described above, according to the present invention, there is provided an operation means for performing an operation using image data of an input line and image data of the same color as the input line read from the line memory, and outputting the operation result. And parameter setting means for setting calculation parameters for each reading of each color, and performing, for example, a weighted average calculation with different parameters for each color, so that an image without color shift can be obtained by moving reading. . That is, by performing read image processing with different parameters for each color, it is possible to realize a low-cost and high-speed read system with good color reproducibility.

According to another feature of the present invention, a numerical value proportional to the reciprocal of the image reduction ratio or the line thinning ratio is used for the predetermined calculation performed on the parameter value used in the previous image data output. Since it is used, moving reading can be performed without color shift even when the image is reduced, and a high-speed and inexpensive color reading system can be provided.

According to another feature of the present invention, there is provided means for changing the lighting time duty of the light source within one cycle of line synchronization for each color to balance the output of each color.
Even when the variation in the brightness of the light source is corrected by adjusting the lighting time, the moving reading can be performed without color shift.

According to another feature of the present invention, edge enhancement is performed with a different edge enhancement amount for each color, and the edge enhancement amount is increased for a low-resolution color. Even when using an inexpensive lens with chromatic aberration that can approach the resolution of each color,
The color reproducibility of the fine black line and the black edge can be improved, and a low-cost reading system with good color reproducibility can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a color scanner according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a document reading position and a parameter according to the first embodiment of the present invention, and is a diagram illustrating an operation of correcting a color shift during moving reading.

FIG. 3 is a flowchart illustrating an interrupt process according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a relationship between a document reading position and a parameter according to a second embodiment of the present invention, and is a diagram for describing an operation of correcting a color shift during moving reading.

FIG. 5 is a flowchart illustrating a parameter determination process according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a process of correcting a color shift amount by adjusting a lighting time according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration example of a color scanner according to a fourth embodiment of the present invention.

FIG. 8 is a diagram illustrating a pixel position in a main scanning direction.

FIG. 9 is a flowchart illustrating an interrupt process according to a fourth embodiment of the present invention.

FIG. 10 is a diagram for explaining edge enhancement processing according to a fourth embodiment of the present invention.

[Explanation of symbols]

 101 Line type sensor unit 102 AD converter 103 Correction circuit 104 Line memory 105 Memory control unit 106 Operation unit 107 DMA interface 108 CPU 109 RAM 110 ROM 111 DMA controller 112 Parameter register 113 Parameter register 114 Timing control unit 115 Color register 116 Color register 704 Line memory 705 Memory control unit 706 Operation unit

Claims (17)

[Claims] 1. An image reading apparatus for obtaining color image data by performing a plurality of readings with a line sensor while changing the emission color of a light source, wherein at least one line of input image data is sequentially output for each color of the light source. A line memory for storing, an operation unit for performing an operation using image data of the input line and image data of the same color as the input line read from the line memory, and outputting the operation result; and an operation in the operation unit. And a parameter setting means for setting the parameters for each reading of each color. 2. The image reading apparatus according to claim 1, wherein the calculation is a weighted average calculation of the image data of the input line and the image data read from the line memory. 3. The image reading apparatus according to claim 2, wherein the parameter of the calculation is a weight of the weighted average. 4. The image reading apparatus according to claim 3, wherein the parameters of the calculation are obtained by performing a predetermined calculation on a parameter value used at the time of outputting the previous image data of the same color. 5. The image reading apparatus according to claim 4, wherein an initial value of the parameter for the calculation is set to a different value for each color. 6. A method according to claim 1, wherein a predetermined operation to be performed on the parameter value used at the time of outputting the previous image data uses a numerical value proportional to an image reduction ratio or a reciprocal of a line thinning ratio. 6. The image reading device according to 5. 7. The image reading apparatus according to claim 5, further comprising means for changing the duty of the light source within one cycle of the line synchronization for each color to balance the output of each color. 8. The image reading apparatus according to claim 7, wherein an initial value of the parameter is determined for each color by using a lighting time duty of each color for calculation. 9. The apparatus according to claim 1, wherein two registers for storing the parameters of the calculation are provided, and the parameters set by the parameter setting means are derived to the calculation means via the two-stage registers. Any one of ~ 8
An image reading device according to the item. 10. An image reading apparatus for obtaining color image data by reading with an image sensor, wherein the output of the image sensor is A / D converted, and the obtained image data is subjected to edge conversion using different parameters for each color. An image reading apparatus, comprising: an arithmetic unit that performs an enhancement operation and outputs the result; and a control unit that controls the edge enhancement degree of a color having a low resolution among the above-described colors so as to increase the edge enhancement degree. 11. The image reading apparatus according to claim 10, wherein the parameter is a coefficient representing the strength of the edge enhancement. 12. The image reading apparatus according to claim 10, wherein two registers for storing the parameters are provided, and the set parameters are derived to the arithmetic means via the two registers. apparatus. 13. An image reading method for obtaining color image data by performing a plurality of readings with a line sensor while changing a light emission color of a light source, wherein parameters used for calculation are set and set for each reading of each color. An image characterized by performing an operation for each reading of each color by using image data of an input line and image data of one line before the same color as the input line according to a parameter, and outputting the operation result. Reading method. 14. The image reading method according to claim 13, wherein the calculation is a weighted average calculation of the image data of the input line and the image data of the previous line of the same color as the input line. 15. An image reading method for obtaining color image data by reading with an image sensor, wherein edge enhancement of a low-resolution color is performed on image data obtained by AD-converting the output of the image sensor. An image reading method characterized in that an edge emphasis calculation is performed with different parameters for each color so as to increase the degree and output. 16. An image reading apparatus that obtains color image data by performing a plurality of readings with a line sensor while changing a light emission color of a light source, wherein the image data of an input line and the previous line of the same color as the input line are obtained. A program for causing a computer to function as a calculation means for performing a weighted average calculation using image data and outputting the calculation result and a parameter setting means for setting parameters of the calculation in the calculation means for each reading of each color. A computer-readable recording medium characterized by being recorded. 17. An image reading apparatus for obtaining color image data by reading with an image sensor, wherein the output of the image sensor is A / D converted, and the obtained image data is subjected to edge conversion using different parameters for each color. A computer-readable program for recording a program for causing a computer to function as arithmetic means for performing an enhancement operation and outputting the same, and control means for controlling the edge enhancement degree of a low-resolution color among the above-mentioned colors so as to increase the degree of edge enhancement; Possible recording medium.