JP2000004366A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of monochromic reading without increasing the reading time, and to improve the quality of a reproduced image. SOLUTION: An original 4 is irradiated with a white light source 1, and a three line color CCD sensor 2 receives the reflected light and converts it into an electric signal. In such a case, an effective storage period (integration period) is controlled by using an electronic shutter function for each line sensor 3a to 3c of the CCD, and subsequently the addition of each color signals is performed in a color correction circuit 14. According to this, for instance, luminance signal can be produced easily. A monochromic image is reproduced by using the luminance signal.

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, and more particularly, to an image reading apparatus having a color reading mode and a monochrome reading mode.

[0002]

2. Description of the Related Art In an image reading apparatus of a type that uses a white light source as a light source and reads a color image using a three-line color CCD of three colors of RGB, when reading in a monochrome mode, green (G) is usually used. )
The original is read by using only the CCD output of.

[0003]

In a color image reading apparatus, when only a green (G) signal is used at the time of monochrome reading, a dropout color (dropout color) is delicate due to a difference in spectral characteristics of a green CCD. However, for example, there is a tendency that a problem occurs in that the reproducibility of red information such as vermilion varies.

Further, since the wavelength range covered by the green (G) signal is limited, when an original of a color (for example, red or blue) distant from the green (G) peak wavelength is read, an image is reproduced. In some cases, it is necessary to reproduce an image that is uncomfortable when viewed from human visual characteristics, such as that the image becomes extreme (it becomes uniformly black or white, or becomes invisible in halftones).

As a countermeasure described above, attention is paid to the color correction function of the color reading signal of the color image reading apparatus, and even in the monochrome mode, each signal of R, G, and B is read in the same manner as in the case of color reading. May be input to a color correction circuit to perform correction to reduce the above-described problem. However, in order to perform processing via the color correction circuit,
Even in the monochrome reading mode, the same time as in the color reading mode is required, and a new problem that the reading time is increased occurs.

The present invention has been made in view of such a problem, and has as its object to improve the accuracy of monochrome reading without increasing the reading time and improve the quality of a reproduced image.

[0007]

To solve the above-mentioned problems, the present invention adopts the following constitution.

According to a first aspect of the present invention, there is provided an image reading apparatus comprising: a white light source for illuminating an object to be read; a three-line color CCD with a shutter function for converting reflected light from the object to be read into an electric signal; Shutter function control means for controlling the shutter function of the three-line color CCD; an A / D converter for converting an analog signal of each color output from the three-line color CCD with the shutter function into a digital signal; Signal synthesizing means for synthesizing digital signals of respective colors obtained through the converter to form a signal for monochrome image reproduction.

[0009] Even in the monochrome reading mode, R,
Utilizing G and B color signals, combining them to obtain a signal for monochrome image reproduction, and individually controlling the substantial charge storage time of each color CCD using an electronic shutter function It is. As a result, the amount of information that is lost (dropped out) during reading can be reduced. Further, it is possible to finely adjust the reading characteristics of the apparatus in the monochrome (mono color) reading mode. Therefore, the reproducibility of a monochrome image is improved.

According to a second aspect of the present invention, in the first aspect of the present invention, the signal synthesizing means also serves as a color correction circuit for performing a product-sum operation in a color reading mode to correct a color shift. The configuration was adopted.

Thus, the color image reading apparatus adds the signals of the respective colors using the color correction circuit originally provided, so that it is not necessary to provide a special circuit in the signal processing path, and the apparatus is not complicated. .

According to a third aspect of the present invention, there is provided the image reading apparatus according to the first or second aspect.
A read signal of each color of red (R), green (G), and blue (B) is obtained from the line color CCD, and the shutter function control means outputs the signals of red (R), green (G), and blue (B). The shutter function of each color CCD is controlled so that the substantial charge storage time of each color CCD is substantially the same as the ratio of the multiplication coefficient of each color in the product-sum operation for generating a luminance signal.

Thus, it is possible to easily generate a luminance signal (a signal having a wavelength component compatible with the characteristics of the human eye and suitable for reproducing a monochrome image). Compared to the case where image reproduction is performed using only the green (G) signal, the signal has a wider dynamic range and a wider color coverage, which is effective in preventing color dropout.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the shutter function is not turned on for the green (G) CCD, and the reading time of one line is set to the green (G). Also, the CCD is configured to be shorter than when the shutter function is turned on.

When the shutter is released for green (G) and other R and B signals are added to this G signal, the total signal level becomes larger than that of the G signal alone. Paying attention to this point, the accumulation time of the CCD of each color is shortened so that the signal amplitude becomes equal to that of the case of the G signal alone while the ratio of the signals of R, G, and B is kept as it is. This allows
The period for reading one line can be shortened while securing the signal amplitude necessary for image processing, and a higher-speed monochrome image can be read.

According to a fifth aspect of the present invention, there is provided an image reading apparatus comprising: a white light source for illuminating an object to be read; a three-line color CCD for converting reflected light from the object to be read into an electric signal; and each color output from the CCD. An A / D converter for converting the analog signal into a digital signal, a product-sum operation means for performing a product-sum operation on the signals of each color output from the three-line color CCD to form a signal for monochrome image reproduction, And coefficient holding means for holding coefficients used for the product-sum operation.

R, obtained from a three-line color CCD,
A desired product-sum operation is performed on the G and B color signals to form an optimal signal required for monochrome image reproduction. Therefore, the reproducibility of a monochrome image is improved. Further, by arbitrarily selecting the holding coefficient, fine adjustment of the read signal can be freely performed.

According to a sixth aspect of the present invention, there is provided an image reading apparatus comprising: a white light source for illuminating an object to be read; a three-line color CCD for converting reflected light from the object to be read into an electric signal; and each color output from the CCD. An analog-to-digital (A / D) converter that converts the analog signal into a digital signal; and a pseudo-luminance signal generating unit that performs a product-sum operation on the signals of each color output from the three-line color CCD to form a pseudo-luminance signal. Configuration.

Since a monochrome image is reproduced using a signal similar to a luminance signal, color dropout can be reduced as compared with a case where only a G signal is used. Further, it is easy to generate a signal.

According to a seventh aspect of the present invention, in the image reading apparatus according to the sixth aspect, the pseudo-luminance signal generating means multiplies a coefficient represented by 1/2 ⁿ (n is a natural number of 1 or more). The configuration was used as a coefficient.

When synthesizing a signal for reproducing a monochrome image, the coefficient used is limited to 2 to the nth power (n = -1, -2,...) So that the product-sum operation can be performed by a bit conversion unit (shift register). And can be realized only by the adder.
As a result, the hardware can be simplified and downsized.

According to an eighth aspect of the present invention, in the image reading apparatus according to the seventh aspect, the pseudo luminance signal generating means includes a bit converter and an adder.

Thus, the hardware can be simplified and downsized.

[0024]

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings.

FIG. 1 shows a main configuration of an apparatus (color copier or color facsimile apparatus) including a color image reading section and an image recording processing section for processing a read signal and recording an image (reproducing an image). FIG.

The color image reading unit includes a white light source 1 such as a fluorescent lamp and a three-line color CCD with a shutter function.
(Contact image sensor) 2. here,
The "shutter function" means that "the electric charge accumulated in an arbitrary period in the scanning period of one line can be discarded by an electrical operation, and thereby, the light accumulation time of the CCD (integral time) in the scanning time of one line" Time) can be adjusted arbitrarily.

The "three-line color CCD" used in the present embodiment has three line sensors 3a, 3b and 3c to which R, G and B color filters are added.

The light of the white light source 1 is the object to be read (original) 4
The reflected light is incident on the image sensor 2 and is converted into an electric signal corresponding to each of R, G, and B colors.

The CCD driving unit 5 is provided with an image sensor 2
To control the drive of. The shutter control unit 6 uses the C
It controls the shutter function of the CD, and has a function of arbitrarily setting an effective integration time for signals of RGB colors.

The signal processing section includes an analog signal processing circuit 8
, A / D converter 9 and shading correction circuit 10
A line-to-line correction circuit 11 and a line memory 12,
An MTF correction circuit 13, a color correction circuit 14, a multi-valued image information memory 15, a CMYK conversion circuit 16, and a recording memory 17 are provided.

The analog signal processing circuit 8 amplifies a signal (read signal) output from the image sensor 2 and performs noise removal by filtering. A / D
The converter 9 converts an analog read signal into a digital signal.

The shading correction circuit 10 corrects the variation in the CCD output (white correction). The line-to-line correction circuit 11 corrects a shift in the reading position of the three-line color CCD. The line memory 12 is provided to temporarily hold data when performing line-to-line correction. The MTF correction circuit 13 performs correction for enhancing the edges of the image (edge enhancement correction).

The color correction circuit 14 performs color correction by performing a product-sum operation (linear conversion) using, for example, a 3 × 3 matrix in the color image reading mode. Is provided to correct the color misregistration. However, in the present embodiment, by utilizing the signal addition function of the color correction circuit, the signals of each color of RGB obtained from the three-line color CCD are combined to produce a monochrome (mono color) image.
A signal for reproducing an image is formed.

The multi-level image information memory 15 is a memory for temporarily storing multi-level image signals. The CMYK conversion circuit 16 performs conversion from RGB space to CMYK space. The recording memory 17 is a memory for temporarily storing the output of the CMYK conversion circuit 16.

The image recording section 18 has a recording control section 18 and a recording head 19. The control unit 7 controls the overall operation of the apparatus (the operation of each unit described above).

In the present embodiment, in the monochrome reading mode, instead of using only the green (G) reading signal as in the related art, all the R, G, and B signals are used, and the shutter function is used. By controlling the charge accumulation time (integration time) of each color CCD, fine adjustment of image reproducibility (dropout color) is performed, and desired reading performance is realized.

For example, when a manufacturer ships a product,
Compensate for variations in the characteristics of the CCD image sensor to make the reading performance uniform, or compensate for variations that occur when the CCD image sensor is replaced when the product is repaired, or intentionally set the desired reading characteristics. Can be easily realized by electrical control using the electronic shutter function of the CCD.

Hereinafter, the operation of the image reading apparatus shown in FIG. 1 (the reading operation in the monochrome (monocolor) reading mode) will be specifically described.

When the document (object to be read) 4 is transported to a predetermined reading position, the white light source 1 irradiates the surface of the document 4. The R, G, and B line sensors 3a, 3b, and 3c of the image sensor 2 convert light reflected from the original into electric signals.

In the present embodiment, when photoelectric conversion is performed by the line sensors (3a to 3c) of the RGB colors, the shutter control unit 6 converts a luminance signal (a signal having a wavelength distribution consistent with the characteristics of human eyes). The effective integration period of each line sensor is controlled at the same ratio as the ratio for generation. Then, a luminance signal is generated by adding the signals of the respective colors by the color correction circuit 14, and this luminance signal is used as a signal for reproducing a monochrome (monocolor) image. The luminance signal is green (G)
Since the wavelength coverage range (dynamic range) is wider than that of the signal alone, it is effective in preventing color dropout. Further, by using the generation ratio of the luminance signal, it is possible to easily generate a monochrome read signal consistent with human eyes.

The luminance signal (L) depends on human visual characteristics and the like.
Can be expressed by the following equation.

L = 0.3R + 0.6G + 0.1B R, G, B line sensors 3a
3c is controlled.

Hereinafter, each line sensor 3a to 3a will be described with reference to FIG.
The shutter control and the generation of the luminance signal in 3c will be specifically described.

The line synchronization signal shown at the top of FIG. 2 indicates the beginning of a period for reading one line of a document (to be read). In the drawing, times t1 to t2 are a reading period of one line. In the period from time t1 to t2,
A period shown in black in FIG. 2 is a period in which the shutter is on (that is, a period in which charge accumulation (integration) is invalidated).

In this embodiment, the ratio of the shutter-off period for each color sensor during the scanning time of one line is R: G: B = 0.3: 0.6: 0.1.

That is, as is apparent from FIG. 2, when the entire period (time t1 to t2) for reading one line is "10", for the red (R), "7" is the shutter-on period. And “3” is the shutter-off period. Therefore, the amplitude (level) of the red (R) image signal (G1) on the first line is a level corresponding to “3” when the dynamic range is “10” (the maximum level is L1).

Similarly, for the green (G) signal, "4"
Is a shutter-on period, and “6” is a shutter-off period. Therefore, the amplitude (level) of the green (G) image signal (G1) on the first line is a level corresponding to "6" when the dynamic range is "10" (the maximum level is L2).

Similarly, for the blue (B) signal, "9"
Is a shutter-on period, and “1” is a shutter-off period. Therefore, the amplitude (level) of the blue (B) image signal (B1) on the first line is a level corresponding to “1” when the dynamic range is “10” (the maximum level is L3).

The signals (R1, G1, B1) of the obtained RGB colors are summed up in this way, and the luminance signal "S1"
Is obtained. Such an addition operation is executed by using a 3 × 3 matrix in the color correction circuit 14 of FIG.

That is, in the color correction circuit 14, the following matrix is prepared in advance for processing at the time of monochrome reading.

(Equation 1)

The sum of the R, G, and B signals (ie, the luminance signal) is output as a green (G) signal. Then, the green (G) output from the color correction unit is
This is a value obtained by taking the sum of the R, G, and B signals. In the subsequent processing, only the green (G) signal is treated as a monochrome read signal.

As described above, according to the present embodiment, it is possible to easily generate a luminance signal that matches the human visual characteristics by performing the linear conversion processing in the shutter control of the image sensor and the color correction circuit. Reproducibility is improved. Further, by appropriately controlling the on-time of the shutter for each color, fine adjustment of the color dropout can be easily performed. In addition, by changing the 3 × 3 matrix in the color correction circuit, each RG
The ratio of B can be arbitrarily changed, and the dropout color can be finely adjusted.

(Embodiment 2) In this embodiment, the shutter is completely turned off when reading green (G) while maintaining the ratio for generating the luminance signal as it is, thereby enabling the RGB colors to be read. Increase the total integration time of The reading time of one line is reduced by utilizing the rise in the level of the reading signal, and the monochrome image is read at a higher speed than in the above-described embodiment. Will be described. In the embodiment described above, in the scanning time of one line, the ratio of the shutter-off period for each color sensor is matched with the coefficient for generating a luminance signal, and R: G:
B = 0.3: 0.6: 0.1. However, in the present embodiment, the shutter is completely turned off for green (G). Therefore, the ratio is adjusted so that the green (G) read signal becomes “1” while the relative ratio of the signals of the respective colors remains unchanged.

That is, R: G: B = 1/2: 1: 1 /
The integration time of the line sensor of each color is controlled by the shutter control circuit 6 of FIG. Then, as shown in FIG. 3, the amplitude (level) of the red (R) image signal (G1) on the first line is “5” when the dynamic range is “10” (the maximum level is L1). It is a level equivalent to.

Similarly, the amplitude (level) of the green (G) image signal is a level corresponding to “10” when the dynamic range is “10” (the maximum level is L2).

Similarly, the amplitude (level) of the blue (B) image signal is a level corresponding to “1.7” when the dynamic range is “10”.

Then, the RGB output from the color correction circuit is output.
The sum value of each signal (that is, the value of the luminance signal S1) is 1.67 times (1/2 +) the output level of the green (G) signal alone.
1 + 1/6). That is, as shown at the bottom of FIG. 3, the level of the luminance signal S1 exceeds the maximum level “L4” in the above-described embodiment and rises to “L5”. However, the level of the luminance signal is “L
A level of "4" is sufficient.

Therefore, this time, the conventional one-line scanning time (time t1 to t2 in FIG. 3) serving as a reference is set to 1 / 1.6.
The reading time for one line is reduced by seven times (about 0.6 times).

FIG. 4 shows this state. As shown at the top and second from the top of FIG. 4, in the embodiment described above,
The reading period of one line is a period from time t1 to t2 (=
"A"). However, in the present embodiment, the reading period of one line is shortened to “A / 1.67”, and high-speed reading is performed. That is, the reading period of one line is shortened to times t1 to t3. In this case, the level of the luminance signal (H-S1) returns to "L4", but it is a sufficient level for a read signal, and no problem occurs. The control of the reading time of one line is as follows.
This is performed by the CCD driving section 5 in FIG.

The integration times of the R, G, and B signals are appropriately set so that the total sum of the RGB signals is equal to or exceeds the level of the green (G) signal alone.
By controlling, the dropout color can be easily adjusted.

(Embodiment 3) FIG. 5 is a diagram showing a main configuration of an image reading apparatus according to the present embodiment. As shown in the figure, the image reading apparatus according to the present embodiment has substantially the same configuration as the above-described embodiment, and includes a white light source 1, a three-line color CCD 2, a CCD driving unit 5, a control unit 7,
An analog signal processing circuit 8, an A / D converter 9, a shading correction circuit 10, an inter-line correction circuit 11, a line memory 12, an image signal synthesis circuit 20, a coefficient holding circuit 21, and an MTF correction circuit 13 Is provided. 1 are denoted by the same reference numerals, and the configuration after the MTF circuit in FIG. 1 is omitted.

The configuration of the present embodiment differs from the configuration of FIG. 1 in that the shutter control of the CCD line sensors 3a to 3c is not performed, and instead, the image signal synthesizing circuit 20 is used.
In the above, the product-sum operation is performed using the holding coefficient of the coefficient holding circuit 21 to generate a signal for monochrome image reproduction.

Image synthesis circuit 20 and coefficient holding circuit 21
Can be formed, for example, by partially modifying the color correction circuit 14 in FIG. 1 or partially adding a new function.

That is, each of the line sensors 3a to 3c of each color of the image sensor 2 outputs all signals accumulated during the reading time of one line. Then, the image signal synthesizing circuit 20 converts the signal of each color of RGB into
A product-sum operation is performed using a coefficient preset in the coefficient holding circuit 21 to generate a composite signal (for example, a luminance signal) for reproducing a monochrome image. By registering a desired coefficient in the coefficient holding circuit 21, it is possible to easily synthesize a luminance signal. For example, “0.3”, “0.6”, “0.
A luminance signal can be easily generated by multiplying each of the RGB signals by the coefficient of “1” and adding the signals. Similarly, fine adjustment of the dropout color can be easily performed.

In the signal synthesis, as described above, when the reading speed is the same as the normal speed, the sum of the coefficients for each of the RGB signals of the coefficient holding circuit 21 is set to 1.0, and the high-speed reading is performed. In the case of implementation, the sum of the coefficients is set to exceed 1.0. In the latter case, high-speed reading of a reciprocal multiple of the sum of the coefficients becomes possible.

According to the present embodiment, there is an advantage that the reproducibility of a monochrome image can be improved even when an image sensor having no shutter function is used.

(Embodiment 4) FIG. 6 is a diagram showing a main configuration of an image reading apparatus according to the present embodiment. As shown, the image reading apparatus of the present embodiment has substantially the same configuration as the apparatus shown in FIG. 5, and includes a white light source 1, a three-line color CCD 2, a CCD driving unit 5, a control unit 7,
, An analog signal processing circuit 8, an A / D converter 9, a shading correction circuit 10, and an inter-line correction circuit 11
, Line memory 12 and pseudo-luminance signal generation circuit 22
And an MTF correction circuit 13. FIG.
1 are denoted by the same reference numerals, and the configuration after the MTF circuit in FIG. 1 is omitted.

A feature of the present embodiment is that a pseudo luminance signal generation circuit is provided instead of the image signal synthesis circuit 20 and the coefficient holding circuit 21 of FIG.

That is, the image reading apparatus is usually provided with a color correction circuit for calibrating a color shift factor depending on the apparatus. However, some devices such as a color scanner have a simple configuration in which correction of color misregistration is performed only by a personal computer that receives a read signal. For such a simple device that does not have a color correction circuit, it is costly to add a new image signal combining unit that generates a luminance signal by a product-sum operation.
There is also a considerable disadvantage in terms of device size.

Therefore, in this embodiment, a circuit 22 for generating a pseudo-luminance signal approximating a luminance signal is provided, and an image signal (pseudo-luminance signal) suitable for monochrome reproduction with a relatively simple and small-scale circuit. Is to be generated.

The feature of the pseudo-luminance signal generation circuit 22 is that, when synthesizing an image signal, its coefficient is represented by R: G: B = 1/2:
1: fixed to 1/4, or the coefficient for each color,
This is to limit the coefficient to a power of 2 n (n = -1, -2...). In other words, by limiting the coefficients required for synthesizing the image signal to those that can be expressed by 2 n, the product-sum operation unit can be realized only by the bit conversion unit and the adder for each of the RGB signals. Hardware simplification and miniaturization are realized.

Next, an example of the configuration of the pseudo luminance signal generation circuit 22 will be specifically described with reference to FIGS. 7 and 8A and 8B.

As shown in FIG. 7, the pseudo-luminance signal generation circuit includes an R bit conversion circuit 23 and a B bit conversion circuit 2.
4, an adder 25, and a clamp circuit 26. Hereinafter, R: G: B = 1/2: 1: close to the luminance signal
The operation will be described by taking as an example a case where signals of respective colors are combined at a fixed ratio of 1/4.

As shown in FIG. 8A, the input RG
The number of bits of each signal of B is 8 bits. Then, the R bit conversion circuit 23 receives the input 8-bit red (R).
The lower one bit of the signal is deleted, and the value is halved. Further, the B bit conversion circuit 24 deletes the lower 2 bits of the input 8-bit blue (B) signal, and reduces the value to １ ／. No bit shift is performed for the green (G) signal.

The adder 25 calculates the sum of the RGB signals after the bit conversion. The addition result is １ ／ · R + G + 1
/ 4 · B, and the spectral distribution is similar to a luminance signal in a pseudo manner. FIG. 8B illustrates the processing algorithm of the pseudo-luminance signal generation unit described above.

Further, in the present embodiment, the output value of the adder 25 is 1.6 times larger than the normal value (at the time of monochromatic RGB signals). When the addition result exceeds 8 bits, the clamp circuit 26 functions to clamp the addition result to a maximum value of 8 bits (0xFF).

As described above, in the present embodiment, the value of each signal is easily changed by the bit shift, so that the calculation using the coefficient is not required. In this case, coefficients required for synthesizing the image signals are 2 to the power of n (n = -1, -2).
..), The degree of freedom of the calculation is limited. However, the sum-of-products operation unit calculates
This can be realized only by the bit conversion unit and the adder for the B signal, so that there is an advantage that the hardware can be simplified and downsized.

[0078]

As described above, according to the present invention, the function inherent in the color image reading apparatus is utilized,
Alternatively, fine adjustment to the dropout color can be easily performed by adding a very simple configuration. Therefore, the reproducibility of a monochrome image can be improved. Further, the total light amount can be easily increased as compared with the case where monochrome reading is performed using only the G light source, and this can be used to improve the reading speed of one line.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an image reading device according to a first embodiment of the present invention;

FIG. 2 is a diagram illustrating an example of an operation of an electronic shutter in the image reading device according to the first embodiment.

FIG. 3 is a diagram for explaining another example of the operation of the electronic shutter in the image reading device according to the first embodiment;

FIG. 4 is a diagram illustrating the principle of high-speed reading in the image reading apparatus according to the first embodiment;

FIG. 5 is a diagram illustrating a configuration of an image reading apparatus according to a second embodiment;

FIG. 6 is a diagram illustrating a configuration of an image reading device according to a third embodiment;

FIG. 7 is a block diagram illustrating a configuration of a pseudo-luminance signal generation circuit.

FIG. 8A is a diagram schematically showing the contents of an operation for each of the RGB signals. FIG. 8B is a diagram schematically showing the contents of a process for generating a pseudo-luminance signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 White light source 2 3 line color image sensor 3a, 3b, 3c RGB line sensor 4 Original (reading object) 5 CCD drive unit 6 Shutter control unit 7 Control unit 8 Analog signal processing circuit 9 A / D converter 10 Shading correction circuit REFERENCE SIGNS LIST 11 line-to-line correction circuit 12 line memory 13 MTF correction circuit 14 color correction circuit 15 multi-valued image information memory 16 CMYK conversion circuit 17 recording memory 18 recording control unit 19 recording head

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 9/07 H04N 1/04 D 5C077 // H01L 27/148 1/40 D 5C079 H01L 27/14 BF Term (reference) 4M118 AA10 AB01 BA10 DB01 FA08 FA50 GC08 5B047 AB02 AB04 BB03 BC06 CA23 CB05 5C051 AA01 BA03 BA04 DB01 DE01 DE19 EA01 5C065 AA00 BB06 BB10 BB48 CC01 CC10 DD16 DD19 EE06 GG18 GG30 GG30 5A07Q20 MP08 PP31 PQ12 5C079 HA13 HB01 HB04 JA23 JA25 MA11 NA01 NA11

Claims (8)

[Claims] 1. A white light source for illuminating an object to be read, a three-line color CCD with a shutter function for converting reflected light from the object to be read into an electric signal, and a shutter function for controlling the shutter function of the three-line color CCD Control means, an A / D converter for converting an analog signal of each color output from the three-line color CCD with a shutter function into a digital signal, and synthesizing a digital signal of each color obtained through the A / D converter And a signal synthesizing means for forming a signal for reproducing a monochrome image by performing the following. 2. The image reading apparatus according to claim 1, wherein a color correction circuit that performs a product-sum operation in a color reading mode to correct a color shift is used as the signal combining unit. 3. A read signal for each of red (R), green (G), and blue (B) is obtained from the three-line color CCD, and the shutter function control means outputs a red (R), green (G) signal. ), Blue (B) shutter function for each color CCD so that the substantial charge accumulation time of each color CCD is substantially the same as the ratio of the multiplication coefficient of each color in the product-sum operation for generating a luminance signal. The image reading device according to claim 1, wherein the image reading device controls: 4. The method according to claim 1, wherein the shutter function is not turned on for the green (G) CCD, and the reading time for one line is shorter than when the shutter function is turned on for the green (G) CCD. The image reading device according to claim 3, wherein 5. A white light source for illuminating an object to be read, a three-line color CCD for converting reflected light from the object to be read into an electric signal, and an A for converting an analog signal of each color output from the CCD into a digital signal. / D converter, sum-of-products calculating means for performing a sum-of-products operation on each color signal output from the three-line color CCD to form a signal for monochrome image reproduction, and holding a coefficient used in the sum-of-products calculation An image reading apparatus, comprising: 6. A white light source for illuminating an object to be read, a 3-line color CCD for converting reflected light from the object to be read into an electric signal, and an A for converting an analog signal of each color output from the CCD into a digital signal. An image reading apparatus, comprising: a / D converter; and a pseudo-luminance signal generating unit that performs a product-sum operation on signals of respective colors output from the three-line color CCD to form a pseudo-luminance signal. 7. The quasi-luminance signal generating means includes: 1/2 ⁿ
7. The image reading apparatus according to claim 6, wherein a coefficient represented by (n is a natural number of 1 or more) is used as a multiplication coefficient. 8. An image reading apparatus according to claim 7, wherein said pseudo-luminance signal generating means includes a bit converter and an adder.