JP2001086351A - Color image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily maintain the correspondence in input image signals and output image signals, even if the spectroscopic characteristics of a light source changes with time by changing a conversion coefficient used for correction so as to dissolve the aging changes in the spectroscopic characteristics of the light source, corresponding to the lighting time of the light source for illuminating an original. SOLUTION: At conversion, a CPU 113 inside a system control unit 112 functions as a conversion coefficient change means and selects a conversion coefficient group, corresponding to the lighting time of fluorescent lamps 31 and 32 from among the plural conversion coefficient groups stored in a RAM 115. For instance, whether the cumulative lighting time of the fluorescent lamps 31 and 32 becomes a prescribed time is decided. Then, every time the cumulative lighting time of the fluorescent lamps 31 and 32 reaches this time, the conversion coefficient group corresponding to the cumulative lighting time of the fluorescent lamps 31 and 32 from among the conversion coefficient groups stored in the RAM 115 is selected and written to the latch of respective coefficient-holding circuits. As a result, coefficient signals outputted by the respective coefficient-holding circuits are updated, so as to dissolve the aging changes in the spectroscopic characteristics of the fluorescent lamps 31 and 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color image reading device. More specifically, after optically reading a document image to obtain a plurality of input image signals forming a set of basic colors,
The present invention relates to an apparatus for converting a plurality of image signals while performing hue correction to obtain a plurality of output image signals forming another set of basic colors. Such a color image reading apparatus is used, for example, as a part of a digital color copying machine.

[0002]

2. Description of the Related Art Recently, in this type of color image reading apparatus, a rare gas white fluorescent lamp is used as a light source for illuminating an original in view of high luminous efficiency and stability with temperature. Things are increasing.

However, when a rare gas white fluorescent lamp is used, if the lamp is used continuously, as shown by an arrow in FIG. 15, the output near blue decreases from I ₀ to I ₁ , and the spectral characteristics of the light source are reduced. Changes with time.

For this reason, even if the correspondence between the input image signal and the output image signal is good at the beginning of use, FIG.
As shown in FIG. 1, if the use is continued for a long time, there is a problem that the error (color shift amount) ΔE between the input image signal and the output image signal increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color image reading apparatus which can maintain a good correspondence between an input image signal and an output image signal even if the spectral characteristics of a light source change with time.

[0006]

According to a first aspect of the present invention, there is provided a color image reading apparatus for optically reading a document image to obtain a plurality of input image signals forming a set of basic colors. After that, in a color image reading apparatus that obtains a plurality of output image signals that form another set of basic colors by converting the image signals while performing correction, the color image reading apparatus according to the lighting time of the light source that illuminates the original, It is characterized by comprising a conversion coefficient changing means for changing a conversion coefficient used for the correction so as to eliminate a temporal change of the spectral characteristic of the light source.

In the color image reading apparatus according to the first aspect,
The conversion coefficient changing means changes the conversion coefficient used for the correction so as to eliminate the change over time of the spectral characteristics of the light source according to the lighting time of the light source illuminating the document. Even if it does, the correspondence between the input image signal and the output image signal is well maintained.

[0008] According to a second aspect of the present invention, there is provided a color image reading apparatus.
2. The color image reading device according to claim 1, further comprising: a storage unit that stores a plurality of groups of conversion coefficients according to a lighting time of the light source for eliminating a temporal change of a spectral characteristic of the light source. The conversion coefficient changing unit selects a conversion coefficient group corresponding to the lighting time of the light source from among the plurality of conversion coefficient groups stored in the storage unit.

In the color image reading apparatus according to the second aspect,
The storage means stores a plurality of groups of conversion coefficients according to the lighting time of the light source for eliminating the temporal change of the spectral characteristics of the light source. Then, the conversion coefficient changing unit selects a conversion coefficient group according to the lighting time of the light source from the plurality of conversion coefficient groups stored in the storage unit. Therefore, even if the spectral characteristics of the light source change with time, the correspondence between the input image signal and the output image signal is maintained well.

[0010] According to a third aspect of the present invention, there is provided a color image reading apparatus.
3. The color image reading device according to claim 1, wherein an accumulated lighting time is used as the lighting time of the light source.

In the color image reading apparatus according to the third aspect,
Since the accumulated lighting time is used as the lighting time of the light source, the correspondence between the input image signal and the output image signal is obtained regardless of whether the light source is continuously turned on or intermittently turned on. Is well maintained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 2 shows a schematic configuration of a mechanical section of a digital copying machine according to an embodiment to which the color image reading apparatus of the present invention is applied, and FIG. 7 shows a block configuration of an electric section of the copying machine.

Referring first to FIG. 2, a document 1 is placed on a platen (contact glass) 2, illuminated by fluorescent lamps 3 ₁ and 3 ₂ as light sources, and a first mirror 4 which can move its reflected light. _1, is reflected by the second mirror 4, _second and third mirror 4 _3, through the imaging lens 5, dichroic enters the click prism 6, wherein three wavelengths of light, red (R), green (G) and blue ( B), and the split light enters the CCDs 7r, 7g, and 7b, which are solid-state imaging devices. That is, red light is on the CCD 7r, green light is on the CCD 7g, or blue light is on the CCD 7b.
Respectively. The outputs of these CCDs 7r, 7g, 7b are output as basic colors R, G, B (hereinafter referred to as "read colors").
Call. ) Is an input image signal.

[0015] Fluorescent lamp 3 _1, 3 ₂ and the first mirror 4 ₁ and the second mirror 4 ₂ is mounted on the first carriage 8 is the third mirror 4 ₃ mounted on the second carriage 9, a second carriage 9 is first 1
By moving to half the speed of the carriage 8, the optical path length from the document 1 to the CCD is kept constant, and the first and second carriages are scanned from right to left when reading the original image. The first carriage 8 is connected to a carriage drive wire 12 wound around a carriage drive pulley 11 fixed to the shaft of the carriage drive motor 10, and the wire 12 is wound around a moving pulley (not shown) on the second carriage 9. As a result, the first carriage 8 and the second carriage 9 move forward and backward (return) by the forward / reverse rotation of the motor 10, and the second carriage 9 moves to half of the first carriage 8. Moving at speed.

When the first carriage 8 is at the home position shown in FIG. 2, the first carriage 8 is detected by a home position sensor 39 which is a reflection type photo sensor. This detection mode is shown in FIG. When the first carriage 8 is driven rightward by the exposure scan and deviates from the home position, the sensor 39 does not receive light (carriage is not detected),
When the first carriage 8 returns to the home position by return, the sensor 39 receives light (carriage detection). When the sensor 39 changes from non-light reception to light reception, the carriage 8 is stopped.

Referring now to FIG. 7, the CCDs 7r, 7
The outputs of g and 7b are converted from analog to digital and subjected to necessary processing in the image processing unit 100, so that black (BK), yellow (Y) and magenta (M ) And cyan (C) (hereinafter, these are referred to as “recorded colors”). These output image signals are respectively supplied to the laser drivers 110bk, 110y, and 110b.
m and 110c, and the respective laser drivers energize the semiconductor lasers 43bk, 43y, 43m and 43c, thereby emitting laser light modulated by recording color signals (output image signals).

Referring back to FIG. The laser light emitted from each of the semiconductor lasers is
bk, 13y, 13m and 13c are reflected by fo
Through the lenses 14bk, 14y, 14m and 14c,
Reflected by the fourth mirrors 15bk, 15y, 15m, and 15c and the fifth mirrors 16bk, 16y, 16m, and 16c, the polygon mirror 17c is a cylindrical lens 17b that is tilted.
After passing through k, 17y, 17m and 17c, the photosensitive drums 18bk, 18y, 18m and 18c are irradiated to form images.

The rotating polygon mirrors 13bk, 13y, 13m, and 13c are provided with polygon mirror driving motors 41bk, 41y, and 41c.
The motors are fixed to the rotating shafts m and 41c, each motor rotates at a constant speed, and drives the polygon mirror to rotate at a constant speed. By the rotation of the polygon mirror, the laser light is scanned in a direction perpendicular to the rotation direction (clockwise) of the photosensitive drum, that is, in a direction along the drum axis.

FIG. 4 shows the laser scanning system of the cyan recording apparatus in detail. 43c is a semiconductor laser. At one end of the laser scanning (two-dot chain line) in the direction along the axis of the photosensitive drum 18c, a sensor 44c composed of a photoelectric conversion element is provided so as to receive laser light.
c detects the laser beam, and detects the start point of one-line scanning at the time when the detection is changed from detection to non-detection. That is, the laser light detection signal (pulse) of the sensor 44c is processed as a laser scanning line synchronization pulse. The configurations of the magenta recording device, the yellow recording device, and the black recording device are exactly the same as the configuration of the cyan recording device shown in FIG.

Referring to FIG. 2, the surfaces of the photosensitive drums are charged scorotrons 19bk, 19y, 19m and 1m connected to a negative voltage high voltage generator (not shown).
9c uniformly charges. When the laser beam modulated by the recording signal is applied to the uniformly charged photoreceptor surface, the charge on the photoreceptor surface flows to the device ground of the drum main body due to a photoconductive phenomenon and disappears. Here, the laser is not turned on in a portion where the document density is high, and the laser is turned on in a portion where the document density is low. As a result, the portions of the surfaces of the photosensitive drums 18bk, 18y, 18m and 18c corresponding to the portions where the document density is high have a potential of -800V.
A portion corresponding to a portion where the density of the document is light is about -100 V, and an electrostatic latent image is formed corresponding to the density of the document.
Each of the electrostatic latent images is referred to as a black developing unit 20b.
k, the yellow developing unit 20y, the magenta developing unit 20m, and the cyan developing unit 20c, and the photosensitive drums 18bk, 18y, 18m, and 18
Black, yellow, magenta, and cyan toner images are formed on the surface of c, respectively.

The toner in the developing unit is positively charged by stirring, and the developing unit is biased to about -200 V by a developing bias generator (not shown), and adheres to a place where the surface potential of the photosensitive member is lower than the developing bias. Then, a toner image corresponding to the document is formed.

On the other hand, the recording paper 27 stored in the transfer paper cassette 22 is fed out by the feeding operation of the feed roller 23, and is sent to the transfer belt 25 at a predetermined timing by the registration roller 24. The recording paper placed on the transfer belt 25 sequentially passes below the photosensitive drums 18bk, 18y, 18m, and 18c as the transfer belt 25 moves, and passes through the photosensitive drums 18bk, 18y, 18m, and 18c. During this time, the black, yellow, magenta, and cyan toner images are sequentially transferred onto the recording paper by the action of a transfer corotron (transfer charger) below the transfer belt. The transferred recording paper is then sent to a heat fixing unit 36, where the toner is fixed to the recording paper,
The recording paper is discharged to a tray 37.

On the other hand, the residual toner on the photoreceptor surface after the transfer is
Cleaner units 21bk, 21y, 21m and 21
Removed by c.

The cleaner unit 21bk for collecting black toner and the black developing unit 20bk are connected by a toner collecting pipe 42, and the black toner collected by the cleaner unit 21bk is collected in the developing unit 20bk. The yellow, magenta, and cyan toners collected by the cleaner units 21y, 21m, and 21c are transferred to the photosensitive drum 18y by, for example, reverse transfer of black toner from recording paper during transfer. No toner is collected for reuse.

Each developing unit is provided with a toner density sensor 45bk, 45y, 45m, 45c, and a signal is output to a toner density control unit (not shown) according to the toner density of each developing unit. The toner density control unit is provided in each developing unit according to the output of each toner density sensor in order to replenish the toner consumed for forming a toner image and keep the toner density of each developing unit constant. The toner supply signals for driving the toner supply motors not to be output are output independently. Toner supply rollers 46bk, 46y, 46m, and 46c are fixed to the rotation shaft of each toner supply motor, respectively. The respective toner supply rollers follow the toner supply signal, and toner is supplied to each developing unit. You.

The recording paper is transferred from the photosensitive drums 18bk to 18c.
The transfer belt 25 sent in the direction of
It is stretched around the drive roller 27, the idle roller 28, and the idle roller 30, and is driven to rotate counterclockwise by the drive roller 27. The drive roller 27 is pivotally attached to a left end of a lever 31 pivotally attached to a shaft 32. Lever 31
A plunger 35 of a black mode setting solenoid (not shown) is pivotally attached to the right end of the solenoid. A compression coil spring 34 is disposed between the plunger 35 and the shaft 32, and the spring 34 applies a clockwise rotational force to the lever 31.

When the black mode setting solenoid is not energized (color mode), as shown in FIG. 2, the transfer belt 25 on which the recording paper is placed is moved to the photosensitive drums 44bk, 44y, 44.
m and 44c. In this state, when the recording paper is placed on the transfer belt 25 and toner images are formed on all the drums, the toner images of the respective images are transferred onto the recording paper as the recording paper moves (color mode). When the black mode setting solenoid is energized (black mode), the lever 31 rotates counterclockwise against the repulsive force of the compression coil spring 34, the drive roller descends 5 mm, and the transfer belt 25 4
4y, 44m and 44c.
bk remains in contact. In this state, since the recording paper on the transfer belt 25 only contacts the photosensitive drum 44bk, only the black toner image is transferred to the recording paper (black mode). At this time, since the recording paper does not contact the photosensitive drums 44y, 44m, and 44c, the recording paper does not adhere to the photosensitive drums 44y, 44m, and 44c (residual toner), and stains such as yellow, magenta, and cyan. Does not appear at all. In other words, copying in the black mode provides a copy similar to that of a normal single-color black copying machine.

FIG. 5 shows the appearance of the console board 300 provided in the apparatus shown in FIG. Referring to FIG. 5, the console board 300 includes a copy start key 30.
1, a numeric keypad 302, a clear / stop key 303, an interrupt key 304, a set number display 305, a copy number display 306, and a touch panel display 307. The touch panel display 307 is provided with a panel in which a number of transparent contact detection switches are arranged on the display surface of the display, and the display unit and the input unit are integrated. Specifically, selection of various operation modes, display of input guidance associated therewith, and display of the selected operation mode are performed by the touch panel display.

Next, the operation timing of the main part of the copying mechanism will be described with reference to the time chart shown in FIG. FIG.
Is for making two identical full color copies. When the fluorescent lamps 3 ₁ and 3 ₂ are turned on and exposure scanning of the first carriage 8 is started, first, the black density reference plate 47 and the white density reference plate 48 shown in FIG. 2 are read, and shading is performed based on the read density. Correction is performed. Next, at substantially the same timing as the start of the scanning of the original placing portion, the modulation bias of the laser 43bk based on the recording signal is started, and the lasers 43y, 43m and 43c are respectively driven by the photosensitive drums 44bk, 44y, 44m and The transfer times Ty, Tm and T of the transfer belt 25 for a distance of 44c.
The modulation energization is started with a delay of c. Transfer charger 2
9bk, 29y, 29m and 29c are energized after a delay of a predetermined time (a time at which the laser irradiation position on the photosensitive drum reaches the transfer charger) from the start of the modulation energization of the lasers 43bk, 43y, 43m and 43c, respectively. I do.

Next, reference will be made to FIG. 7 showing the outline of the electrical unit of the copying machine. The electrical unit is mainly provided with a reading processing unit 101, an image processing unit 100, an image recording unit 108, a synchronization control unit 111, and a system control unit 112.

The reading processing unit 101 reads a document image. More specifically, the input image signals output from the CCDs 7r, 7g, 7b are converted into 10-bit digital signals by A / D converters 102r, 102g, 102b, respectively, and input to the shading correction circuit 103. The shading correction circuit 103 corrects unevenness of illuminance of the CCD reading optical system, variation in sensitivity of the light receiving element group in each CCD, and dark current, and outputs 10-bit reading color gradation signals R, G, B. I do.

The image processing unit 100 includes a γ correction circuit 1
04, a color correction circuit 105, a scaling processing circuit 106, and a dither processing circuit 107.

The gamma correction circuit 104 performs logarithmic conversion on the input read color gradation signals R, G, and B, and corrects gradation characteristics in accordance with an instruction from the console 300.
R, G, and B read color density signals Dr, D of 8 bits each
Output g and Db.

The color correction circuit 105 performs a masking process and outputs R, G, and B input signals Dr, Dg, and Db.
With the recording colors C (cyan), M (magenta), and Y
(Yellow) and BK (black) signals (corresponding to the recording density of each toner) Dc, Dm, Dy and Dbk. In this conversion, basic color correction for correcting the deviation of the recording characteristics of the apparatus from the ideal characteristics,
And arbitrary color correction based on an instruction from console board 300 is performed. The configuration and operation of the color correction circuit 105 will be described later in detail.

The 8-bit recording color density signals Dc, Dm, Dy and Dbk output from the color correction circuit 105 are:
It is applied to the scaling processing circuit 106. Magnification processing circuit 106
Performs a scaling process in the main scanning direction (a direction perpendicular to the direction of movement of the first carriage 8) on each color signal in response to an instruction from the console board 300, and outputs an 8-bit recording color density signal Dc ', Dm', Dy 'and Dbk' are output. Note that the magnification in the sub-scanning direction (the moving direction of the first carriage 8) is changed by changing the moving speed of the first carriage 8.

The signal output from the scaling processing circuit 106 is applied to a dither processing circuit 107. The dither processing circuit 107 performs dither processing on the recording density signals Dc ′, Dm ′, Dy ′, and Dbk ′, and outputs 3-bit recording color gradation signals C, M, Y, and BK. In this dither processing, correction of the non-linear characteristic on the gradation of the recording system is also performed.

The image recording unit 108 energizes the semiconductor lasers 43c, 43m, 43y and 43bk according to the recording color gradation signals C, M, Y and BK output from the image processing unit 100. The signal of BK is given to the laser driver 110bk as it is, but the signals Y,
M and C are buffer memories 109y and 109, respectively.
m and 109c, the delay time T shown in FIG.
It is read after y, Tm and Tc and applied to laser drivers 110y, 110m and 110c.

The synchronization control unit 111 synchronizes the timing of signal transmission / reception between the reading processing unit 101, the image processing unit 100, and the image recording unit 108, and between elements in each unit.

The system control unit 112 has a CPU
(Central processing unit) 113, ROM (read only memory) 114, RAM (random access memory) 115, I / O (input / output) ports 1000, 11
6, 117, 118, 119 and 120, and controls the entire copying machine. In particular, this system control unit 112
Is the lamp lighting circuit 10 via the I / O port 1000.
01 by controlling the lights up or turns off the fluorescent lamp 3 _1, 3 _2. Also, the system control unit 112 has an I / O
A display control of the console board 300 and a key input operation detection process are performed via the port 116, and a predetermined operation is performed according to the key input.

FIG. 1 shows a specific configuration of the color correction circuit 105 shown in FIG. Referring to FIG. 1, the color correction circuit 105
Includes a hue area determination circuit 121, a black extraction circuit 122, a black removal circuit 123, and a masking circuit 124.

The hue area determination circuit 121 is a circuit for identifying to which of the plurality of predetermined areas the hue indicated by the input read color density signals Dr, Dg, Db belongs. It is output as a hue identification signal Sarea.

The black extraction circuit 122 generates a signal Dbk for determining the recording density of the black toner component from the input read color density signals Dr, Dg, Db. Ink extraction circuit 12
The contents of the processing of No. 2 are basically expressed by the following equation (1), and processing according to the processing mode of black extraction (such as full black and skeleton black) and the UCR rate is added.

Dbk = BKr · Dr + BKg · Dg + BKb · Db (1) In the expression (1), DKr, BKg, and BKb are constants, and are automatically switched according to the state of the hue identification signal Sarea.

The black removal circuit 123 corrects the recording color density signals Dr, Dg and Db based on the recording color density signal Dbk output from the black extraction circuit 122. The content of the correction is basically expressed by the following equation (2), and further includes processing according to the black extraction mode and UCA processing.

Dr ′ = Dr−Dbk Dg ′ = Dg−Dbk Db ′ = Db−Dbk (2) The masking circuit 124 outputs the read color density signals Dr ′ and Dg ′.
And Db ′, the signals Dc, Dm and Dy representing the respective recording densities of the recording cyan toner, magenta toner and yellow toner are generated. An error based on the difference between the actual characteristics and the ideal characteristics of the recording system is corrected by this masking process. The color adjustment based on the instruction from the operator is also executed by this masking process. The processing content of the masking circuit 124 is expressed by the following equation (3).

Dc = KCr ・ Dr ′ + KCg ・ Dg ′ + KCb ・ Db ′ Dm = KMr ・ Dr ′ + KMg ・ Dg ′ + KMb ・ Db ′ Dy = KYr ・ Dr ′ + KYg ・ Dg ′ + KYb ・ Db ′ (3) , KCr, KCg, KCb, KMr, KMg, KMb, K
Yr, KYg and KYb are constants, and the hue identification signal Sar
It is automatically switched according to the state of ea.

FIG. 8 shows the details of the configuration of the above-mentioned hue area determination circuit 121. Referring to FIG. 8, the hue region determination circuit 121 includes a hue coding circuit 125, a boundary hue holding circuit 126, a hue comparison circuit 127, and a coding circuit 128.
It is composed of

The hue coding circuit 125 generates an 8-bit hue code corresponding to the hue indicated by the read color density signals Dr, Dg and Db based on the read color density signals Dr, Dg and Db. The boundary hue holding circuit 126 includes eight 8-bit data H ₁ , H ₂ , H ₃ ,
It has a function of holding and outputting H ₄ , H ₅ , H ₆ , H ₇ and H ₈ . These eight 8-bit data H ₁ , H ₂ ,
H ₃ , H ₄ , H ₅ , H ₆ , H ₇ and H ₈ are arranged in order in advance so as to satisfy the following equation (4).

H ₁ ≧ H ₂ ≧ H ₃ ≧ H ₄ ≧ H ₅ ≧ H ₆ ≧ H ₇ ≧ H ₈ (4) The hue comparison circuit 127 converts the 8-bit code H output from the hue coding circuit 125 into The eight 8-bit data H ₁ , H ₂ , H ₃ , H ₄ ,
Compared with each of H ₅ , H ₆ , H ₇ and H ₈ , it outputs eight double signals indicating the magnitude relation of each.

The coding circuit 128 includes the hue comparison circuit 12
The combination of the states of the eight double signals output by 7 is coded as shown in FIG. 9 and output as a 3-bit signal Sarea. Here, eight 8-bit data H ₁ , H ₂ , H ₃ , H ₄ , H ₅ , H ₆ , and 8 outputted by the boundary hue holding circuit 126 are output.
Since H ₇ and H ₈ are previously arranged in descending order, the combinations of the states of the eight signals output by the hue comparison circuit 127 are nine in form. However, the case where all the signals indicating the comparison results are L (H> H ₁ ) and the case where all the signals are H (that is, H ≦ H ₈ ) can be regarded as the same hue region due to the periodicity of the hue. There are actually eight types of combinations of signals output from the hue comparison circuit 127, which can be encoded into three bits.

In this embodiment, by referring to the 3-bit signal Sarea, it is possible to identify which of the eight types of regions the hue of the input image signal (combination of Dr, Dg, Db) belongs to. I do.

FIG. 10 shows the configuration of the black extraction circuit 122 in detail. Referring to FIG. 10, the black extraction circuit 122 includes a coefficient holding circuit 129, multipliers 130r, 130g, and 130.
b, adders 131 and 132, and a black adjustment circuit 133.

The coefficient holding circuit 129 outputs three signals bk
r, bkg and bkb are output simultaneously. These signals are respectively represented by the coefficients BKr and BKg of the above-mentioned equation (1).
And BKb, each of which has a 10-bit sign. The coefficient holding circuit 129 simultaneously stores each coefficient in 8
One set is selected and output according to the hue identification signal Sarea. That is, the coefficients BKr, B
Kg and BKb are set independently for each hue region. The eight sets of coefficients held by the coefficient holding circuit 129 are written by the system control unit 112. Therefore, the system control unit 112 sets the coefficient BK
r, BKg and BKb are updated as needed.

The multiplier 130r outputs the signals Dr and bkr,
Multiplier 130g outputs signals Dg and bkg to multiplier 130g.
b multiplies the signals Db and bkb, respectively, and outputs the upper 12 bits of the result. Further, adder 131 adds the output signal of multiplier 130g and the output signal of multiplier 130b and outputs the result, and adder 132 adds the output signal of multiplier 130r and the output signal of adder 131. . Accordingly, a value corresponding to the calculation result on the right side of the above equation (1) is obtained as the output of the adder 132. The black adjustment circuit 133 detects an overflow of the value output from the adder 132,
Underflow correction and system control unit 112
Performs a process according to the signal BPmode indicating the black extraction mode and the UCR rate in accordance with the instruction from. Then, the processing result is output as a signal Dbk.

FIG. 11 shows a part of the configuration of the masking circuit 124 in detail. Referring to FIG. 11, the circuit includes nine multipliers 141 to 149 and three adders 150.
~ 152 are provided. The multiplier 141 outputs the coefficient signal KC
r and the density signal Dr ', the multiplier 144 multiplies the coefficient signal KCg and the density signal Dg', the multiplier 147 multiplies the coefficient signal KCb and the density signal Db ', and
42 multiplies the coefficient signal KMr by the density signal Dr '; a multiplier 145 multiplies the coefficient signal KMg by the density signal Dg'; a multiplier 148 multiplies the coefficient signal KMb by the density signal Db '; The detector 143 includes a coefficient signal KYr and a density signal D.
r ′, the multiplier 146 multiplies the coefficient signal KYg by the density signal Dg ′, and the multiplier 149 generates the coefficient signal KYb.
And the density signal Db '. The adder 150
Outputs the sum of the signals output from the multipliers 141, 144 and 147, and the adder 151 outputs
5 and 148 output the sum of the signals output, and adder 152 outputs the sum of the signals output by multipliers 143, 146 and 149. That is, the adders 150 and 15
Numerals 1 and 152 output Dc, Dm and Dy of the calculation result shown in the above equation (3), respectively.

The masking circuit 124 is provided with a coefficient holding circuit 160 as shown in FIG. 12 for applying the coefficient signal KCr to the input terminal of the multiplier 141. Although not shown for simplicity, the coefficient signals KMr to KY are supplied to the other multipliers 142 to 149, respectively.
To apply b, a coefficient holding circuit having the same configuration as that of the coefficient holding circuit 160 is provided.

Referring to FIG. 12, coefficient holding circuit 160
Is composed of data selectors 161 and 170 and eight 10-bit latches 162 to 169. Each 10-bit input terminal of each of the eight latches 162 to 169 is commonly connected to a 10-bit data line DATA connected to an output terminal of the system control unit 112. Also,
The respective latch control terminals of the eight latches 162 to 169 are connected to the data selector 161. Input terminals (TP, SEL) of the data selector 161 are connected to signal lines TP, S connected to output terminals of the system control unit 112.
Connected to EL.

The signal line SEL output by the system control unit 112 among the eight latches 162 to 169
The latch pulse appearing on the signal line TP is selectively applied to one of the latches determined by the value of, and the coefficient data on the data line DATA is latched. Therefore,
The system control unit 112 has eight latches 162 to
169 can be written with any 10-bit signed data.

The output terminals of the eight latches 162 to 169 are connected to different input terminals of the data selector 170, respectively. The 3-bit selection control terminal of the data selector 170 includes the hue region determination circuit 121 described above.
Is applied. The data selector 170 outputs one of the 10-bit signed data latched by the eight latches 162 to 169 according to the hue identification signal Sarea.

That is, the coefficient holding circuit 160 holds the eight independent coefficients written by the system control unit 112, and according to the hue identification signal Sarea,
One of the eight coefficients is selected and output as a coefficient signal KCr.

The coefficient signal KCr output from the coefficient holding circuit 160 and the coefficient signals KMr to KYb similarly output from other coefficient holding circuits (not shown) are applied to the input terminals of the multipliers 141 to 149 shown in FIG. Is done.

The coefficient data written in the latches 162 to 169 of the coefficient holding circuits (160 and the like) are stored in the RAM 115 in the system control unit 112 in advance. More specifically, the RAM 115 stores in advance information about changes in spectral characteristics (time-dependent changes in spectral characteristics) with the lapse of the lighting time of the original illumination fluorescent lamps 3 ₁ and 3 ₂ . Further, the RAM 115, for eliminating the time course of the spectral characteristics of the fluorescent lamp 3 _1, 3 _2, the fluorescent lamp 3 _1, 3 conversion coefficient set in accordance with the _second cumulative lighting time is more group storage.

At the time of actual conversion, the system control unit
CPU 113 in 112 works as conversion coefficient changing means
Of the plurality of conversion coefficient groups stored in the RAM 115
Fluorescent light 3₁, 3_TwoSelect a conversion coefficient group according to the lighting time of
You. In this example, as shown in FIG.₁, 3_Two
The cumulative lighting time of the predetermined time (for example, 50h, 100h,
(200h, 400h) is determined (S
1). And fluorescent light 3 ₁, 3_TwoThe cumulative lighting time of
Each time the number of conversion managers stored in the RAM 115
Fluorescent light 3 out of several groups₁, 3_TwoConversion according to cumulative lighting time
A coefficient group is selected, and the coefficient of each coefficient holding circuit (160, etc.) is
162-169. As a result, each coefficient
The coefficient signals KCr to KYb output from the road are₁,
3_TwoHas been updated to eliminate the aging of the spectral characteristics of
You.

Therefore, even if the spectral characteristics of the fluorescent lamps 3 ₁ and 3 ₂ change over time, as shown in FIG. 14, for example, every time the cumulative lighting time reaches 50 h, 100 h, 200 h, and 400 h, the reading color R, G, B and recording colors C, M, Y, BK
The error (color shift amount) ΔE corresponding to the above is reduced. Therefore, the correspondence between the read colors R, G, and B and the recording colors C, M, Y, and BK can be maintained well, and highly accurate color correction can be performed.

It should be noted, because of the use of the accumulated lighting time as a lighting time of the fluorescent lamp 3 _1, 3 _2, if the fluorescent lamp 3 _1, 3 ₂ is continuously lit, either when it is intermittently turned , The reading colors R, G, B and the recording colors C, M, Y, BK
Can be maintained satisfactorily. However, the cumulative lighting time for each copy mode may be adopted as the cumulative lighting time.

[0067]

As is apparent from the above description, in the color image reading apparatus of the first aspect, the conversion coefficient changing means eliminates the temporal change of the spectral characteristics of the light source according to the lighting time of the light source illuminating the original. So as to change the conversion coefficient used for the correction between the input image signal and the output image signal,
Even if the spectral characteristics of the light source change over time, the correspondence between the input image signal and the output image signal can be maintained well.

In the color image reading apparatus of the second aspect, the conversion coefficient changing means selects a conversion coefficient group corresponding to the lighting time of the light source from among the plurality of conversion coefficient groups stored in the storage means. Even if the spectral characteristics of the image signal change with time, the correspondence between the input image signal and the output image signal can be maintained well.

In the color image reading apparatus according to the third aspect, since the accumulated lighting time is used as the lighting time of the light source, either the case where the light source is continuously turned on or the case where the light source is intermittently turned on is used. However, the correspondence between the input image signal and the output image signal can be favorably maintained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a color correction circuit of a copying machine according to an embodiment to which a color image reading device of the present invention is applied.

FIG. 2 is a diagram showing a schematic configuration of a mechanical section of the copying machine.

FIG. 3 is a diagram illustrating a mode in which a first carriage is detected by a home position sensor of the copying machine.

FIG. 4 is a diagram showing in detail a laser scanning system of the cyan recording device of the copying machine.

FIG. 5 is a diagram showing an overview of a console board of the copying machine.

FIG. 6 is a diagram showing operation timings of main parts of the copying machine.

FIG. 7 is a block diagram illustrating a schematic configuration of an electrical unit of the copying machine.

FIG. 8 is a diagram illustrating a configuration of a hue region determination circuit in the color correction circuit.

FIG. 9 is a diagram showing a correspondence between an input and an output of a coding circuit in the hue region determination circuit.

FIG. 10 is a diagram showing a configuration of a black extraction circuit in the color correction circuit.

FIG. 11 is a diagram showing a configuration of a masking circuit in the color correction circuit.

FIG. 12 is a diagram illustrating a configuration of a coefficient holding circuit in the masking circuit.

FIG. 13 shows that the CPU in the system control unit
Among the plurality of conversion coefficient groups stored in M, the fluorescent lamps 3 ₁ and 3 ₂
FIG. 4 is a diagram showing a flow of selecting a conversion coefficient group according to the lighting time of the present invention.

FIG. 14 shows the error (color shift amount) ΔE between the read colors R, G, B and the recording colors C, M, Y, BK in the copying machine.
FIG. 7 is a diagram showing a lapse of time.

FIG. 15 is a diagram illustrating a change over time in spectral characteristics of a rare gas white fluorescent lamp.

FIG. 16 shows a corresponding error (color shift amount) ΔE between reading colors R, G, B and recording colors C, M, Y, BK in a conventional apparatus.
FIG. 7 is a diagram showing a lapse of time.

[Explanation of symbols]

3 ₁ , 3 ₂ light source 100 image processing unit 101 reading processing unit 108 image recording unit 111 synchronization control unit 112 system control unit

Continued on the front page F-term (reference)

Claims (3)

[Claims] An image of a document is optically read to obtain a plurality of input image signals forming a set of basic colors, and then these image signals are converted while forming corrections to form another set of basic colors. In a color image reading apparatus for obtaining a plurality of output image signals, a conversion for changing a conversion coefficient used for the correction so as to eliminate a temporal change of a spectral characteristic of the light source according to a lighting time of a light source for illuminating the document. A color image reading device comprising a coefficient changing unit. 2. The color image reading device according to claim 1, wherein a plurality of groups of conversion coefficients according to a lighting time of the light source are stored for eliminating a temporal change of a spectral characteristic of the light source. Means for selecting a conversion coefficient group corresponding to a lighting time of the light source among a plurality of conversion coefficient groups stored in the storage means. 3. The color image reading device according to claim 1, wherein an accumulated lighting time is used as the lighting time of the light source.