JP2000125093A - Digital copying machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a read image and a print image of high quality by the digital copying machine which is provided with a scanner mode or high picture quality mode by improving the S/N. SOLUTION: A scanner part 13 reads a document by an image sensor, an image processing part processes the read image data, and a printer part 21 prints the image data. When the scanner mode is selected by an external device or console panel 2 which are connected to the digital copying machine, the read speed of the scanner part 13 in the vertical scanning direction is made slower than in copy mode. Consequently, the image data can be inputted to the external device without mounting a large-capacity memory storing image data and a read image of high picture quality with high read precision can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital copying machine, and more particularly, to a digital copying machine having an image reading device having a line image sensor and sequentially reading a document line by line.

[0002]

2. Description of the Related Art Conventionally, a digital copying machine generally has a scanner section for reading image data. The scanner portion of this conventional digital copying machine has been used only for copying. However, some recent digital copiers are multifunctional and have functions such as copying, facsimile, printer, and scanner. The reading speed of the scanner unit in the scanner mode or the copy mode is reading at the same speed.

For example, Japanese Patent Application Laid-Open No. 7-10728 of the prior art 1
As described in the publication, the reading speed of the scanner unit in the copy mode is made to match the writing speed of the printer. In this specification, the image data read by the scanner can be used as it is in the printer unit. In the scanner mode, image data read at the same reading speed as in the copy mode is temporarily stored in the image memory, and the image data is read out from the image memory again and output to the external device.

In Japanese Patent Application Laid-Open No. 2-74968 of the second prior art, the lighting voltage of an exposure lamp and the original scanning speed of a scanning unit are controlled in order to adjust the density of a recorded image. As described above, in recent digital copying machines, image formation has been performed at higher density and higher speed.

[0005]

However, as the speed of image formation increases, it becomes more severe in terms of maintaining high image quality. The higher the speed of the scanner unit, the higher the clock frequency in the image sensor and the subsequent signal processing unit, and the lower the reading accuracy. In addition, there is a factor of deteriorating the reading accuracy in terms of high density.

[0006] For example, consider a case where the resolution changes from 400 dpi to 600 dpi. Assuming that the reading speed in the sub-scanning direction does not change, the main scan 600 dpi and the sub-scan 6
It is necessary to read an image of 00 dpi. For this reason,
2.25 (= (600 × 600) / (400 × 40
0) It is necessary to read at twice the reading speed in the CCD of the image sensor. When attention is paid to the output voltage per pixel of the CCD, the output voltage is proportional to the product of the light quantity and the accumulation time determined by the line cycle. 400 dpi to 600
The number of pixels in the main scanning direction is 1.5
And the amount of light received per CCD pixel is 1 /
1.5. Further, since the line cycle is also 1 / 1.5, the accumulation time is also 1 / 1.5. Therefore, the output voltage per pixel of the CCD is 1 / 2.25 (= 1/1.
5 × 1 / 1.5), which is considerably lower than 400 dpi.

It is necessary to increase the gain by the subsequent signal processing unit. At that time, however, the noise component is also amplified. As a result, the S / N ratio is reduced by the lamp light amount and the reading speed in the sub-scanning direction. In the same case, there is a problem that it becomes worse than 400 dpi.

[0008] At the time of copying in a copying machine, the printing accuracy of the printer is lower, so that there is not much problem. However, in the scanner mode, there is a problem in that a read image having a lower reading accuracy than the conventional one is output as described above.

Further, if the reading speed in the scanner mode is to be read at the same high speed as in the printer mode, the data cannot be taken into an external device in time, so that a large-capacity memory for storing image data as in the prior art is mounted. There is a need to. For this reason, there is a disadvantage that the cost is increased and the size of the apparatus is increased.

FIG. 4 shows the result of measuring random noise with respect to the signal output voltage of the CCD. This noise amount is
It is proportional to the square root of the signal charge. The signal charge is amplified and output as a signal output from the CCD. Therefore, as shown in FIG. 4, the ratio of random noise / signal output decreases as the signal output increases. For this reason, a read image having a higher S / N can be obtained when the signal output is higher. The signal charge amount is proportional to the product of the incident light amount and the accumulation time.
Therefore, since the product of the incident light amount and the accumulation time is 1 / 2.25, as a result, the S / N becomes worse than 400 dpi when the lamp light amount and the reading speed in the sub-scanning direction are the same. I will.

[0011] At the time of copying in a copying machine, the printing accuracy of the printer is lower, so that there is not much problem. However, in the scanner mode, there is a problem that a read image having a lower read accuracy than the conventional one is output as described above. Even at the time of copying, there is a possibility that the recording accuracy of the printer will be improved in the future and the S / N of the scanner will be reduced.

The present invention provides a digital copying machine which is provided with a scanner mode or a high image quality mode, and when this mode is selected, improves the S / N to obtain a high quality read image and print image. The purpose is to do.

The purpose of each claim of the present invention will be described below. According to a first aspect of the present invention, when the scanner mode is selected, the reading speed in the sub-scanning direction of the scanner unit is changed to be slower than that in the copy mode, so that a large-capacity memory for storing image data is not mounted. An object of the present invention is to obtain a high-quality read image that can be taken into an apparatus and has high read accuracy.

According to a second aspect of the present invention, when the reading speed in the sub-scanning direction of the scanner unit is changed between the copy mode and the scanner mode, the read line cycle of the image sensor unit is changed to be slower according to the reading speed. The object of the present invention is to obtain a read image with high read accuracy in which the output voltage per pixel of the CCD can be increased and the S / N is improved as a result.

According to a third aspect of the present invention, a plurality of lines of image data read by the image sensor are stored, and when the reading speed of the scanner section in the sub-scanning direction is changed in the scanner mode, an average of pixels in each main scanning direction from the plurality of lines is obtained. It is an object of the present invention to obtain a read image with high reading accuracy by calculating a value to reduce the variation of each pixel.

According to a fourth aspect of the present invention, a plurality of lines of image data read by the image sensor are stored, and when the reading speed of the scanner section in the sub-scanning direction is changed in the scanner mode, a weight count is set for the plurality of lines, and An object of the present invention is to obtain a read image with high resolution and high read accuracy by calculating pixels in the main scanning direction from image data and weight counts.

According to a fifth aspect of the present invention, when the scanner mode and the high image quality mode are selected, the reading speed of the scanner unit in the sub-scanning direction is changed to be lower than that in the copy mode, thereby obtaining a high quality read image with high reading accuracy. The purpose is to obtain.

According to a sixth aspect of the present invention, when the reading speed of the scanner unit in the sub-scanning direction is changed, the read line cycle of the image sensor unit and the read clock are delayed in accordance with the reading speed, so that the CCD storage time is reduced. It is an object of the present invention to obtain a read image with high S / N and high read accuracy by increasing the output voltage per pixel of the CCD and improving the sampling accuracy.

According to a seventh aspect of the present invention, a read image with high reading accuracy is obtained by changing a sampling method in a signal processing section for sampling an output signal from an image sensor according to a scanner mode, a high image quality mode, and a standard mode. The purpose is to:

According to another aspect of the present invention, the signal processing section for sampling the output signal from the image sensor performs or does not perform correlated double sampling in accordance with the scanner mode, the high image quality mode, and the standard mode. An object is to obtain a read image with high reading accuracy.

[0021]

According to a first aspect of the present invention, there is provided a digital copying machine which controls a scanner section for reading an original by an image sensor and a printer section for printing image data. A digital copying machine having a system control unit, an external device or an operation unit having a function of selecting a copy mode and a scanner mode, and a reading speed of the scanner unit in the sub-scanning direction when the scanner mode is selected. And control means in the system control unit that changes later.

According to a second aspect of the present invention, in the digital copying machine according to the first aspect, when the reading speed of the scanner unit in the sub-scanning direction is changed between the copy mode and the scanner mode, an image is formed according to the reading speed. There is further provided control means for changing the read line cycle of the sensor unit.

According to a third aspect of the present invention, in the digital copying machine of the first aspect, a storage means for storing a plurality of lines of image data read by the image sensor, and a reading speed of the scanner unit in the sub-scanning direction in the scanner mode. Calculating means for calculating an average value of each pixel in the main scanning direction from a plurality of lines when changing.

According to a fourth aspect of the present invention, in the digital copying machine of the first aspect, a storage means for storing a plurality of lines of image data read by the image sensor, and a reading speed of the scanner section in the sub-scanning direction in the scanner mode. The image processing apparatus further includes calculation means for setting a weight count for a plurality of lines when the change is made, and calculating a main scanning direction pixel from the image data and the weight count for the plurality of lines.

A digital copying machine according to a fifth aspect of the present invention is a digital copying machine having a scanner section for reading a document by an image sensor, a printer section for printing image data, and a system control section for controlling the whole. Alternatively, it has a function of selecting a reading mode of the scanner by the operation unit, and the system control unit and the scanner unit have control means for changing the reading speed of the scanner unit in the sub-scanning direction according to the reading mode. .

According to a sixth aspect of the present invention, in the digital copying machine according to the fifth aspect, when the reading speed of the scanner unit in the sub-scanning direction is changed according to the reading mode, the reading clock of the image sensor unit is changed according to the reading speed. And control means for changing the cycle of.

According to a seventh aspect of the present invention, in the digital copying machine according to the fifth aspect, a signal processing unit for sampling an output signal from the image sensor is provided, and a reading speed of the scanner unit in the sub-scanning direction according to a reading mode. When you change
There is control means for changing the sampling method in the signal processing unit.

According to an eighth aspect of the present invention, in the digital copying machine according to the seventh aspect, the switching of the sampling method of the signal processing unit is performed according to the presence or absence of correlated double sampling.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a digital copying machine according to the present invention will be described in detail with reference to the accompanying drawings. Referring to FIGS. 1 to 17, there is shown a digital copying machine according to an embodiment of the present invention.

(Embodiment 1) FIG. 1 shows an internal configuration of a scanner section to which the present invention is applied. The apparatus includes a first carriage 6 including a contact glass 1 on which an original 14 is placed, a halogen lamp 2 for exposing the original, and a first reflecting mirror 3.
A second carriage 7 including a second reflection mirror 4 and a third reflection mirror 5, a lens unit 8 for forming an image on a CCD linear sensor 9, and a white unit for correcting various distortions caused by a reading optical system or the like. And a reference plate 15. During scanning, the first carriage 6 and the second carriage 7 are moved in the sub-scanning direction A by the stepping motor.

FIG. 2 is a block diagram of a color digital copying machine. A scanner unit 13 for reading the original 14 and gamma correction for improving the accuracy of the color correction of the read image data (RGB), color correction for converting the RGB signals into Y, M, C and Bk, and the original 14 Image processing unit 20 having a filter for correcting the image quality to the optimum according to the image, a main scanning scaling function, etc.
Printer unit 21 for printing Y, M, C, Bk image data on paper, and system control unit 23 for controlling the whole
And the operation panel 24 constitute a color digital copying machine 25. In the case of a black-and-white digital copier, there is no color conversion, and only Bk data is output to the printer unit 21.
In the scanner mode, image data (RGB) for which color conversion is not performed is output from the image processing unit 20 to the PC 22.

FIG. 3 shows the color digital copying machine 25 shown in FIG.
3 is a block diagram of an internal configuration of the scanner unit 13 of FIG. First, the original 14 is irradiated by the halogen lamp 2, and the reflected light from the original 14 passes through the first carriage 6 and the second carriage 7, passes through the lens unit 8, is reduced and coupled onto the three-line color CCD sensor 9, It is read every time. The read image signal is received by the sensor board 10, and the image signal is output from the three-line color CCD sensor 9 to the signal processing board 12 in synchronization with the drive pulse on the sensor board 10.

The image signal, which is an analog signal, is input to an analog signal processing circuit 40. Here, the image signal is converted into a continuous analog signal by sampling and holding the image signal with a sample pulse by a sample-and-hold circuit, and the black level correction circuit corrects the variation in the dark output level of the CCD by using a black level correction circuit. Is converted into a signal.

The image signal is an AGC (A) signal for correcting a substantial light amount determined by the relationship between the CCD sensitivity and the illuminance on the document surface.
auto Gain Control). The analog signal output from the analog signal processing circuit 40 is A
The digital signal is converted by the / D conversion circuit 41. In the shading correction circuit 42 at the next stage, the reflected light of the white reference plate 15 irradiated by the halogen lamp 2 is read by the three-line color CCD sensor 9 to obtain a predetermined density level, and the sensitivity variation of the CCD is obtained. And uneven light distribution of the irradiation system. The line-to-line correction circuit 43 corrects the distance between each of the RGB lines in the sub-scanning direction A as described above, and outputs an image signal read at the same position.

The control signal generation circuit 44 generates a control signal and a timing signal for each processing circuit, and transmits a CCD drive pulse to the sensor board 10.

FIG. 4 shows a three-line type color CCD sensor 9.
5 shows the result of measuring random noise with respect to the output of FIG.
This noise amount is proportional to the square root of the signal charge amount. The signal charge is amplified and output as a signal output from the CCD. Therefore, as shown in FIG. 4, the random noise / signal output decreases as the signal output increases. Therefore, a readout image having a higher S / N can be obtained when the signal output is higher. The signal charge amount is proportional to the product of the incident scene and the accumulation time. Therefore, in order to increase the signal charge amount in order to obtain a read image with a good S / N, the incident light amount and the accumulation time may be increased. However, in order to increase the amount of incident light, it is necessary to increase the amount of lamps. However, it is difficult for a copying machine to increase the amount of lamps because power is being saved.

Accordingly, in the present embodiment, when the scanner mode is selected from the PC 22 or the operation panel 24 which is an external device, the system control unit 23
Instructs the scanner 13a to set the reading speed in the sub-scanning direction to a lower reading speed than in the copy mode. Scanner 1
In 3a, the read line cycle of the CCD 9 is switched according to the read speed. If the reading linear speed in the scanner mode at this time is adjusted to the data transfer speed when outputting to the PC 22 as an external device, the memory for speed adjustment can be reduced.

(Embodiment 2) For example, a case where the reading speed in the copy mode is 100 mm / s and the reading speed in the scanner mode is 50 mm / s, which is half the speed in the copy mode, will be described. FIG. 5 shows various timing signal examples 1 for driving the CCD. CC from light receiving section
A shift signal SH for transferring to a D register, and a CCD
Transfer clocks φ1 and φ for transferring charges in registers
2, a driving pulse is generally composed of a pulse RS for resetting an output buffer in the CCD and a CLP for clamping an electrical black level immediately after resetting. The light receiving section continues to receive light during a period from one shift signal SH to the next shift signal SH. This time is called accumulation time.
The transfer clocks φ1 and φ2 are frequencies at which all the pixels of the CCD can be transferred within the accumulation time, and the condition is that the transfer clocks do not move during the active period of the shift signal SH. Vo indicates a signal output from the CCD, and includes a dummy signal idle transfer portion, an optical black portion in which a light receiving portion is shielded, and an effective photocell portion to be actually read.

FIG. 6 shows the timing when the reading speed in the sub-scanning direction is 10 mm / s in the copy mode. The line cycle T1 at this time is 423 μs (= 25.4 / (100 × 600)) when the reading density is 600 dpi,
Becomes

FIG. 7 shows the timing when the reading speed in the sub-scanning direction is 50 mm / s in the scanner mode. The line cycle T2 at this time is 846 μs (= 25.4 / (50 × 600)) when the reading density is 600 dpi. Therefore, the line cycle in the scanner mode can be doubled compared to that in the copy mode. Accordingly, the accumulation time is also doubled, and the signal charge amount of the CCD light receiving unit is doubled. As described above, the signal output from the CCD is also doubled, so that the S / N is improved.

(Embodiment 3) FIG. 8 shows that a character "A" written on a document is being scanned. Arrow B indicates the main scanning direction, and arrow C indicates the sub-scanning direction. First, the image is read by the CCD at the position indicated by the arrow 51 first. At this time, one line is read at the same time, and the direction indicated by arrow 51 indicates the order in which data is read. Next, reading is performed at the position of arrow 52 after 423 μs. When the reading density is 600 dpi, the interval between the arrows is 25.4 / 600 mm. The image read in this way is represented by a bitmap pattern on the memory,
The data is as shown in FIG.

At the time of the scanner mode, the reading speed is reduced by 1 /
Suppose it becomes 2. At this time, assuming that the line cycle does not change, as shown in FIG. 10, the scanning is performed at twice the scanning density as in the copy mode of FIG. That is, the reading density in the sub-scanning direction is 1200 dpi. At this time, referring to FIG. 10, an average value of image data read at the scanning positions indicated by arrows 53 and 54 is calculated for each pixel in each main scanning direction. By doing so, 1200 dpi
To 600 dpi data. Also, by taking the average, the noise for each pixel is also averaged. For this reason,
A read image having an improved S / N compared to the copy mode can be obtained. The above calculation part may be included in the line-to-line correction circuit 43 or may be provided at a subsequent stage.

(Embodiment 4) In the above embodiment, the S / N is improved by a simple calculation called averaging, but there is a side effect that the resolution is reduced by applying a low-pass filter by averaging.

FIG. 11 is a model diagram of correction using cubic function convolution. The pixel row P indicates a pixel row read by an arrow shown in FIG. That is, the arrow r
Indicates a distance in the sub-scanning direction. Pixel row P is 600 dp
One pixel at the time of i is indicated by a line interval of 0.5 pixel.

Here, the image data (density data) of the data Pn in the main scanning direction on the n-th line is converted from the preceding and succeeding four lines of data (P _{n−3 to} P _{n + 3} ) by a cubic function as a weighting function. An example of creation using convolution will be described.

The interpolation function h (r) for each data is determined from the distance r of each data from Pn. This is the correction coefficient. Here, h (r) is represented by three equations shown in FIG. 11 by the distance r from the center in the piecewise cubic polynomial approximation of Sinx / x.

Pn is obtained by multiplying the corresponding coefficient data by the correction coefficient. Further, in order to correct the density unevenness, the sum of the correction coefficients is set to the denominator so that the sum of the correction coefficients becomes 1. That is, the following equation is obtained.

Pn = [P _n−4 × h (−2) + P _n−3 × h
(−1.5) + P _n−2 × h (−1) + P _n−1 × h (−
0.5) + P _n × h (0) + P _{n + 1} × h (0.5) + P
_{n + 2} × h (1) + P _{n + 3} × h (1.5) + P _{n + 4} × h
(2)] / [h (-2) + h (-1.5) + h (-1)
+ H (-0.5) + h (0) + h (0.5) + h (1)
+ H (1.5) + h (2)]

Next, the pixel row of P _{n + 2} two lines later is calculated in the same manner. In this manner, the read data of 1200 dpi is converted into the read data of 600 dpi. At this time, noise can be reduced by the above-described calculation, and a highly accurate read image can be obtained without degradation in resolution.

In the first to fourth embodiments, the reading speed in the scanner mode has been described as being half of the reading speed in the copy mode. However, it is needless to say that the same control can be used for other ratios. Further, the pixel density is not limited to 600 dpi.

FIG. 12 applied to the following fifth to eighth embodiments.
Is different from the scanner 13a shown in FIG. 3 applied to the first to fourth embodiments in that it includes two oscillators 45 and 46. Other configurations are the same.

(Embodiment 5) In this embodiment, the scanner mode is an external device such as the PC 22 or the operation panel 2.
4, when the scanner mode or the high image quality mode is selected, the system control unit 23 instructs the scanner 13b to set the reading speed in the sub-scanning direction to be lower than that in the copy mode. At this time, if the reading linear speed in the scanner mode is adjusted to the data transfer speed at the time of outputting to the PC 22, which is an external device, the speed adjustment memory can be reduced.

(Embodiment 6) For example, a case where the normal reading speed is set to V1 mm / s, the reading speed in the scanner mode and the high image quality mode is set to V2 mm / s, and reading is performed in a relationship of V1> V2 will be described.

FIG. 13 shows various timing signal examples 2 for driving the CCD. A shift signal SH for transferring from the light receiving section to the CCD register, transfer clocks φ1 and φ2 for transferring charges in the CCD register, and CC
Pulse RS for resetting the output buffer in D
A drive pulse is generally composed of a CLP for clamping an electrical black level immediately after reset. The light receiving section continues to receive light during a period from one shift signal SH to the next shift signal SH. This time is called accumulation time. The transfer clocks φ1 and φ2 are frequencies at which all the pixels of the CCD can be transferred within the accumulation time, and the condition is that the transfer clocks do not move during the active period of the shift signal SH. Vo
Denotes a signal output from the CCD, and comprises a dummy signal idle transfer portion, an optical black portion in which a light receiving portion is shielded, and an effective photocell portion to be actually read.

FIG. 14 shows the timing when the reading speed V1 mm / s in the sub-scanning direction in the standard mode. The line cycle T1 at this time is 25.4 / (V1 × 600) sec when the reading density is 600 dpi. At this time, the clock input to the control signal generation circuit 44 in FIG.

FIG. 15 shows the timing in the case of the reading speed V2 mm / s in the sub-scanning direction in the scanner mode or the high image quality mode. The line cycle T2 at this time is 25.4 / (V2 × 60 when the reading density is 600 dpi).
0). At this time, the clock input to the control signal generation circuit 44 in FIG. Accordingly, the line cycle in the scanner mode and the high image quality mode can be made longer than in the standard mode, and accordingly, the accumulation time is doubled, and the signal charge amount of the CCD light receiving unit is doubled. As described above, the signal output from the CCD is also doubled, so that the S / N is improved. Also, the read clock cycle is made longer in the scanner mode and the high image quality mode than in the standard mode. Therefore, C
The time of the signal output portion from the CD becomes longer, the sampling timing can be performed accurately, and a read image with a better S / N can be obtained.

(Embodiments 7 and 8) FIG. 16 is a block diagram of a sampling circuit of the analog signal processing circuit 40. This circuit uses correlated double sampling (CDS: Co
related Double Sampling)
This is a circuit for reducing the noise generated in the CCD, and suppresses the noise by utilizing the correlation between the noises in the field output portion and the signal output portion of the CCD output.

A method of reducing noise by correlated double sampling will be described with reference to FIG. The field through level is clamped by the clamp pulse SHP in the CCD output waveform. In addition, sampling pulse SHD
Sampling the field through level. Similarly, the signal output section is sampled. Finally, the difference between the field through level and the signal output is output from the differential amplifier.

In the CCD output waveform, A, A ', B
And B 'and C' and C 'have strong correlations. Therefore, if the signals are passed through an amplifier in a state where the phases are matched after the sample hold, the noises can be canceled out by canceling each other.

However, when the clock cycle is shortened to 600 dpi, a flat portion of the field through level in the CCD output waveform cannot be obtained, and it becomes difficult to generate the timing of the clamp pulse SHP. For this reason, there is a problem that noise is increased when the correlated double sampling is forcibly performed. Therefore, at the time of normal reading, FIG.
The switch in No. 6 is switched to the GND side so that correlated double sampling is not performed. When the reading clock is switched late in the scanner mode and the high image quality mode, the above-described switch is switched to perform correlated double sampling to obtain a noise-free read image.

[0061]

As is apparent from the above description, in the digital copying machine according to the first aspect, when the scanner mode is selected, the reading speed of the scanner section in the sub-scanning direction is changed to be lower than that in the copy mode. ing. As a result, it is possible to capture the image data into an external device without mounting a large-capacity memory for storing image data, and it is possible to obtain a high-quality read image with high reading accuracy.

According to the second aspect of the present invention, when the reading speed in the sub-scanning direction of the scanner unit is changed between the copy mode and the scanner mode, the read line cycle of the image sensor unit is changed to be slower according to the reading speed. I have. As a result, the accumulation time of the CCD can be lengthened, the output voltage per pixel of the CCD increases, and as a result, a read image with high S / N and high read accuracy can be obtained.

According to a third aspect of the present invention, a plurality of lines of image data read by the image sensor are stored, and when the reading speed of the scanner unit in the sub-scanning direction is changed in the scanner mode, each line is read from the plurality of lines in the main scanning direction. Calculate the average value of the pixels. As a result, it is possible to obtain a read image with high reading accuracy while reducing the variation of each pixel.

According to a fourth aspect of the present invention, when a plurality of lines of image data read by the image sensor are stored and the reading speed of the scanner section in the sub-scanning direction is changed in the scanner mode, a weight count is set for the plurality of lines. A pixel in the main scanning direction is calculated from the image data of a plurality of lines and the weight count.
As a result, a read image with high resolution and high read accuracy can be obtained.

According to the fifth aspect of the present invention, when the scanner mode and the high image quality mode are selected, the reading speed of the scanner in the sub-scanning direction is changed to be lower than that in the copy mode. Therefore, it is possible to obtain a high-quality read image with high reading accuracy.

According to the present invention, when the reading speed of the scanner unit in the sub-scanning direction is changed, the read line cycle of the image sensor unit and the read clock are delayed according to the reading speed. This allows CC
The accumulation time of D can be lengthened, the output voltage per pixel of the CCD increases, the sampling accuracy can be improved, and a read image with high S / N and high read accuracy can be obtained.

According to the seventh aspect of the present invention, the sampling method in the signal processing unit for sampling the output signal from the image sensor is changed according to the scanner mode, the high image quality mode, and the standard mode. Therefore, a read image with high read accuracy can be obtained.

According to the eighth aspect of the present invention, the signal processing section for sampling the output signal from the image sensor selects whether or not to perform correlated double sampling in accordance with the scanner mode, the high image quality mode, and the standard mode. . As a result, a read image with high reading accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is an internal configuration diagram of a scanner unit applied to a digital copying machine according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a block configuration of a color digital copying machine.

FIG. 3 illustrates a scanner section of the color digital copying machine of FIG.
It is a block diagram of the example 1 of an internal structure.

FIG. 4 is a characteristic diagram showing a result of measuring random noise with respect to an output of a CCD.

FIG. 5 shows various timing signal examples 1 for driving a CCD.

FIG. 6 shows a reading speed of 10 m in the sub-scanning direction in the copy mode.
The timing in the case of m / s is shown.

FIG. 7 shows a reading speed 50 in the sub-scanning direction in the scanner mode.
The timing in the case of mm / s is shown.

FIG. 8 shows that a character A written on a document is being scanned.

FIG. 9 is a diagram showing data on a memory of a read image in a bitmap pattern.

FIG. 10 is a diagram showing a state of the scanning density in FIG. 8 when the reading speed is reduced to half in the scanner mode as compared with that in the copy mode.

FIG. 11 shows a model diagram of correction using cubic function convolution.

12 is a diagram illustrating a block configuration of an internal configuration example 2 of the scanner unit of the color digital copying machine in FIG. 1;

FIG. 13 shows various timing signal examples 2 for driving the CCD.

FIG. 14 shows a reading speed V1m in the sub-scanning direction in the standard mode.
The timing in the case of m / s is shown.

FIG. 15 shows timings in the case of a reading speed V2 mm / s in the sub-scanning direction in the scanner mode or the high image quality mode.

FIG. 16 is a block diagram of a sampling circuit of the analog signal processing circuit.

FIG. 17 is a diagram for explaining a noise reduction method by correlated double sampling.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Contact glass 2 Halogen lamp 3 1st reflection mirror 4 2nd reflection mirror 5 3rd reflection mirror 6 1st carriage 7 2nd carriage 8 Lens unit 9 CCD linear sensor (3 line type color CCD sensor) 10 Sensor board substrate 12 Signal Processing board 13 Scanner section 14 Document 15 White reference board 20 Image processing section 21 Printer section 22 PC 23 System control section 24 Operation panel 25 Color digital copier 40 Analog signal processing circuit 41 A / D conversion circuit 42 Shading correction circuit 43 Between lines Correction circuit 44 Control signal generation circuit

Claims (8)

[Claims] 1. A digital copying machine having a scanner section for reading a document by an image sensor, a printer section for printing image data, and a system control section for controlling the whole, has a function of selecting a copy mode and a scanner mode. An external device or an operation unit; and a control unit in the system control unit that changes a reading speed of the scanner unit in the sub-scanning direction when the scanner mode is selected, in comparison with the copy mode. Digital copier. 2. The digital copying machine according to claim 1, wherein when the reading speed of the scanner unit in the sub-scanning direction is changed between the copy mode and the scanner mode, the read line cycle of the image sensor unit is changed according to the reading speed. Digital copier further comprising control means for changing the value of. 3. The digital copying machine according to claim 1, wherein said storage means stores a plurality of lines of image data read by said image sensor, and said image data is read when a reading speed in a sub-scanning direction of a scanner unit is changed in a scanner mode. Calculating means for calculating an average value of each pixel in the main scanning direction from a plurality of lines;
A digital copier further having. 4. The digital copying machine according to claim 1, wherein said storage means stores a plurality of lines of image data read by said image sensor, and said image data is read when a reading speed in a sub-scanning direction of a scanner unit is changed in a scanner mode. A digital copying machine further comprising: a calculating unit that sets a weight count for a plurality of lines and calculates a pixel in the main scanning direction from the image data of the plurality of lines and the weight count. 5. A digital copying machine having a scanner section for reading an original by an image sensor, a printer section for printing image data, and a system control section for controlling the whole, wherein the reading mode of the scanner is set by an external device or an operation section. A digital copying machine having a selection function, wherein the system control unit and the scanner unit have control means for changing a reading speed of the scanner unit in the sub-scanning direction according to a reading mode. 6. The digital copying machine according to claim 5, wherein when the reading speed of the scanner unit in the sub-scanning direction is changed according to the reading mode, the period of the reading clock of the image sensor unit is changed according to the reading speed. Digital copying machine having control means for performing 7. The digital copying machine according to claim 5, further comprising: a signal processing unit that samples an output signal from the image sensor, wherein when the reading speed of the scanner unit in the sub-scanning direction is changed according to the reading mode, A digital copying machine having control means for changing a sampling method in a signal processing unit. 8. The digital copying machine according to claim 7, wherein the switching of the sampling method of the signal processing unit is performed according to the presence or absence of correlated double sampling.