JPH10257209A - Picture reader and copying machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the temperature fluctuation of the optical black part of an image sensor and the fluctuation of dark current noise distribution by controlling the power consumption of the image sensor in accordance with the read signal level of an original. SOLUTION: A controller 3010 detects the level fluctuation of an average value D with the fluctuation of the signal level. When the average value D is D<D0-0.25LSB against the reference value D0, it judges that power is oversupplied at present and operations for dropping the voltage of a driver power source 3011 and for dropping the voltage of a CCD power source 3012 are individually executed or shared. Then, power supply to the CCD image sensor 1100 is controlled to be reduced. When the average value D is D>D0+0.25LSB, the controller 3010 judges that power supply lacks at present. The respective operations are individually executed or shared. Then, power supply to the CCD image sensor 1100 is controlled to be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus, and more particularly, to the heat of an image sensor which can occur when reading an original for a long time, such as continuous reading, using an image sensor such as a CCD image sensor. The present invention relates to an image reading apparatus provided with a means for correcting image quality deterioration due to a temporal change of noise or the like.

[0002]

2. Description of the Related Art In recent years, an image reading apparatus is incorporated in a copying machine, a facsimile, an OCR, or the like, and reads an original image and outputs it to a transmission system, or exposes and transfers a photosensitive member according to a reading signal. Used. At this time, when reading an image using the line image sensor, the area image is read by sequentially scanning the arrangement direction of the line image sensors as the main scanning direction and the relative movement direction between the original and the line image sensor as the sub-scanning direction. ing.

FIG. 7 shows a CC used in a document reading apparatus.
1 shows a configuration of a D-line image sensor. The subject light is photoelectrically converted by a photodiode 11 (hereinafter PD11),
The charges generated here are transferred to the shift gate 12 (hereinafter referred to as SH1).
Is transferred in the direction of the arrow by the transfer register 13 via 2),
The output amplifier 14 outputs a voltage corresponding to the charge amount.

The transfer register 13 has driving pulses φ1, φ2
Is driven in two phases, and the driving pulse is
Supplied from both ends.

A bias current to the output amplifier 14 is a CCD.
The power supply terminal 15 (hereinafter referred to as VO) of the linear image sensor 10
D15).

The power consumption of the CCD linear image sensor 10 is mainly determined by the CCD 3012 shown in FIG.
Output amplifier 14 supplied from power supply via terminal 15
Consumption P1 corresponding to the bias power supply of FIG.
The total is the consumption amount P2 corresponding to the driver power supply supplied from the driver power supply indicated by 011.

[0007] Shift gate SH12, transfer register 13
Is known as a capacitive load, and it is generally known that when the load capacitance C is driven at the frequency f and the voltage V, the power consumption P is expressed by P = CV ² f, and the power P2 is proportional to the driving frequency. Increase.

FIG. 8 shows an equivalent circuit when the transfer register 13 is regarded as a distribution constant. The values of the resistors R1 to R6 are all equal, the values of the capacitors C1 to C5 are all the same, and the power P2 supplied from the driver is consumed by the resistors R1 to R6.

When the driving currents from both ends of the CCD line image sensor are bilaterally symmetric and balanced at the midpoint a, the resistor R1 receives the current for charging and discharging the capacitors C1 to C3, and the resistor R2 receives the capacitor C2. The current for charging / discharging C3 is
A current for charging and discharging the capacitor C3 flows through the resistor R3.

Therefore, the relation of the power consumption P in the resistors R1 to R3 is P (R1)> P (R2)> P (R3).

On the other hand, the power consumed by the shift gate SH12 can be ignored for the following reason.

The shift gate SH12 is driven only when the charge is transferred from the PD 11 to the transfer register 13, and its cycle is very long.
About 1/2000 for the cycle corresponding to the driving frequency of 3
About 1/5000.

Therefore, the power P2 is approximately equal to the transfer register 1
3 can be considered only as electric power.

FIG. 9 shows a CCD linear image sensor 10.
3 shows the power distribution. The power consumption is extremely high near the left end of the output amplifier 14, and has a distribution having another slightly smaller peak at the other end.

The power distribution is equal to the heat generation distribution, and the dark current noise of the CCD linear image sensor 10 has a characteristic of doubling the temperature rise of 8 ° C. Can be considered to be equal to the tendency of the power distribution shown in FIG.

When the CCD linear image sensor 10 is used in the document reading apparatus, it is important to improve the image quality by reducing the local concentration and fluctuation of the dark current noise distribution. To this end, the power consumption shown in the distribution of FIG. It is necessary to disperse heat efficiently.

FIG. 10 shows a conventional example using a heat radiating plate 40. A sufficiently large heat radiating plate 40 is pressed on the opposite side of the light incident surface of the CCD linear image sensor 10 to uniformize the heat distribution in the CCD linear image sensor 10 and increase the heat capacity to improve heat radiation. , CCD
The purpose is to suppress the absolute temperature of the linear image sensor 10.

[0018]

However, in the above-mentioned conventional example, considering that the radiator plate 40 has a finite size and an increase in ambient temperature, driving for a long time is performed as in the case of flowing reading. If so, it may be thermally saturated.

FIG. 11 shows a CCD linear image sensor 1.
0 represents a change in the dark current noise distribution. In general, the CCD linear image sensor 10 has a light-shielded photodiode section (FIG. 11: optical black (OB) section) as a reference for a black level. Is converted.

Therefore, when the distribution of the dark current noise shown in FIG. 11 changes, the signal level in the effective pixel period relatively fluctuates, causing the image to be underexposed or the image to appear whitish. .

The noise near the black level is very noticeable visually, and when the user continuously reads a plurality of originals, the fluctuation of the black level during the reading operation causes fatal image quality deterioration. Effect.

An object of the present invention is to concentrate the power consumption in the vicinity of the OB portion, thereby increasing the temperature in this portion,
The problem is that the dark current increases, and as a result, the clamp level fluctuates, whereby the black level fluctuates and the image does not deteriorate.

[0023]

In order to achieve the above object, the present invention provides a means for measuring a reading signal level of a document, a power consumption varying means for changing power consumption in an image sensor, and a method for reading the document. Means for controlling the power consumption varying means in accordance with a signal level.

Further, the variable means for changing the power consumption of the image sensor changes a power supply voltage to the image sensor, or changes a voltage of a driving power supply to a driver for driving the image sensor. Alternatively, the duty of the driving power supply to the driver for driving the image sensor is changed. In the present invention, these variable means for changing the power consumption are operated together or independently.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a scanner equipped with a color CCD linear image sensor.

The scanner 1000 is the scanner body 10
00a and a document feeder 1000b.

The scanner main body 1000a is configured as follows.

Reference numeral 1010 denotes a platen glass on which an original is mounted, and 1012 denotes a first mirror unit.
It comprises a document exposure halogen lamp 1005 and a first reflection mirror 1002. Reference numeral 1013 denotes a second mirror unit, which is a second reflection mirror 1003,
It comprises a third reflection mirror 1004. Symbol 100
Reference numeral 1 denotes a lens unit for reducing and forming an image of the original reflected light on the color CCD linear image sensor 1100. Reference numeral 1009 denotes a platen glass for drift reading when the document is read by using the document feeder 1000b. Reference numeral 1014 denotes a stepping motor.

The document feeder 1000b is configured as follows.

In FIG. 1, reference numeral 1006 denotes a document input tray, 1007 denotes a document pick-up roller, 1008 denotes a feed roller for feeding a document, 10
Reference numeral 16 denotes a paper discharge roller. Reference numeral 1011 denotes a paper discharge tray.

In the above configuration, the platen glass 101
In the case of reading a document placed on 0, document reading scanning is performed by the following operation.

First, it is assumed that an original is mounted on the platen glass 1010 with the original surface facing down. The mirror units 1012 and 1013 are
In order to keep the optical path length from the document reflection surface to the CCD line image sensor 1100 constant, the scanning is performed in the sub-scanning direction (the direction of arrow A) at a scanning speed of 2: 1. Is scanned.

The lens unit 1001 reduces and forms the light of the halogen lamp 1005 reflected at each sub-scanning position of the document and passed through the reflecting mirror group (1002 to 1004) on the CCD linear image sensor 1100. CC
The D linear image sensor 1100 reads the image formed at each sub-scanning position while scanning the image in the main scanning direction (a direction running through the drawing). Note that the lens unit 1001 and the CCD linear image sensor 1100 are at fixed positions.

In this case, the mirror units 1012 and 10
13 starts from the position indicated by the broken line.

Further, in the above configuration, when reading a document mounted on the input tray 1006,
The original reading scanning is performed by the following operation.

First, it is assumed that an original is mounted on the input tray 1006 with the original surface facing upward.

In the case of reading a single-sided original, the original is read while being conveyed in the direction of the dashed arrow. That is, the feed roller 1007 is
The sheet is fed by a feed roller 1008 in accordance with the reading timing of the document, is conveyed in the direction of the dashed arrow, passes over the platen glass 1009, and is discharged to the discharge tray 1011.

In the case of reading a double-sided document, the document is read while being conveyed in the direction of the solid arrow. That is, first, the document fed by the feed roller 1008 is conveyed in the direction of the solid arrow. Next, after the front side (the front side) passes through the reading position of the platen glass 1009 and is read, the front side is reversed according to the transport path (solid line arrow), and the back side is read in the direction opposite to that at the time of the front side reading. Finally, the paper is conveyed along the paper discharge path (solid arrow) and discharged to the paper discharge tray 1011.

In both the case of reading a single-sided original and the case of reading a double-sided original, similarly to the case of reading an original mounted on the platen glass 1010, the lens unit 1001 is used.
Are reflected at each sub-scanning position of the document and are reflected by a reflection mirror group (100
The light from the halogen lamp 1005 that has passed through 2-1004) is reduced and imaged on the CCD linear image sensor 1100. CCD linear image sensor 1100
Reads the image formed at each sub-scanning position while scanning it in the main scanning direction (the direction running through the drawing). The lens unit 1001 and the CCD linear image sensor 1100
Is in a fixed position.

At this time, the sub-scanning direction of the image formed on the color CCD linear image sensor 1100 is indicated by an arrow B when reading the front side and an arrow C when reading the back side. On the other hand, the main scanning direction is the same in both cases.

FIG. 2 is a configuration diagram of the color CCD linear image sensor 1100.

In FIG. 2, reference numeral 2000 denotes a color CCD linear image sensor.
Reference numeral 003 denotes red, blue, and green CCD linear image sensor units, respectively.

Reference numerals 2001a to 2001c denote linear photodiode arrays having red on-chip color filters, respectively.
Reference numerals a to 2003c denote linear photodiode arrays having blue and green on-chip color filters, respectively.

Reference numerals 2004a to 2004d, 2005a
2005d is a linear photodiode array 2001
a to 2001c are output to each output amplifier 21.
A CCD shift register for horizontal transfer to 01a to 2101d and 2102a to 2102d.

Here, the CCD shift registers 2005a-
2005d is for reading in the forward direction (front side) (in the direction of the solid line arrow in FIG. 2), and is a CCD shift register.
b indicates the left half charge of the linear photodiode array to output amplifiers 2102a and 2102b, and the CCD shift registers 2005c and 2005d indicate the right half charge of the linear photodiode array to output amplifiers 2102c and 210.
The charge is transferred to 2d. CCD shift register 2005
The charge transfer directions of a and b and the CCD shift registers 2005c and d are opposite to each other.

CCD shift registers 2004a-200
4d is for reading in the reverse direction (back side) (in the direction of the dashed arrow in FIG. 2)
Similarly, the linear photodiode array is divided into left and right parts, and charges are transferred to the output amplifiers 2101a to 2101d.

Further, the CCD shift registers 2005a-
2005d is a blue linear photodiode array 200
2a to 2002c are output to an output amplifier 2102
It is also a CCD shift register for horizontal transfer (for reading in the reverse direction of blue) to a to 2102d.

Reference numerals 2006a to 2006d denote CCD shift registers for reading the blue forward direction for transferring the charges generated in the blue linear photodiode arrays 2002a to 2002c to the output amplifiers 2103a to 2103d.

The CCD shift registers 2006a-2006
2006d is a green linear photodiode array 200
It is also a CCD shift register for outputting the charges generated in 3a to 2003c (for reading green in the reverse direction).

Reference numerals 2007a to 2007d denote CCD shift registers for horizontally transferring electric charges generated in the green linear photodiode arrays 2003a to 2003c to the output amplifiers 2104a to 2104d.

Reference numerals 2206, 2207, and 2208 denote shift gates SH1, SH2, and SH3 that transfer charges generated in the linear photodiode array 2001a to the next-stage linear photodiode array 2001b.

This shift gate performs the following operation.

At the time of reading in the forward direction, the charge of the linear photodiode array 2001a is transferred to the shift gate SH1.
(2206) → shift gate SH2 (2207) → shift gate SH3 (2208) → linear photodiode array 2001b, and charge is added in the linear photodiode array 2001b.

At the time of reading in the reverse direction, the charge of the linear photodiode array 2001b is shifted from the shift gate SH3 (2208) → the shift gate SH2 (2207) → the shift gate SH1 (2206), contrary to the reading in the forward direction.
The data is transferred in the order of the linear photodiode array 2001a, and the charge is added in the linear photodiode array 2001a.

Similarly, reference numerals 2209 to 2211 denote shift gates SH4 to SH6 for controlling the charge transfer between the linear photodiode arrays 2001b and 2001c, respectively. Shift gate SH4 → shift gate SH5 →
Shift gate SH6, shift gate SH6 → shift gate SH5 → shift gate SH4.

Reference numeral 2212 denotes a shift gate SH7 for transferring charges generated in the linear photodiode array 2001c to the horizontal CCD shift registers 2005a to 2005d in synchronization with the reading speed of the scanner.

Reference numerals 2213 and 2214 denote shift gates S.
Switch gates SG1 and SG2 for sequentially transferring the charge of the linear photodiode array 2001c transferred by H7 (2212) to the horizontal CCD shift registers 2005a to 2005d for each pixel.

The charge of odd pixels is transferred to the horizontal CCD shift register 200 by the switch gate SG1 (2213).
5a and 5c and transferred to the switch gate SG2 (221
According to 4), the charges of the even-numbered pixels are transferred to the horizontal CCD shift registers 2005b and 2005d.

Reference numerals 2215 to 2217 denote transfer gates TG for transferring electric charges between the horizontal CCD shift registers 2005a and 2005b and between the horizontal CCD shift registers 2005c and 2005d.
1 to TG3.

Transfer of charges by the shift gate between the linear photodiode arrays described above (for example, shift gates SH1 (2206), SH2 (2207), S2 between linear photodiode arrays 2001a and 2001b)
Similarly to H3 (2208), the transfer gate TG1 → the transfer gate TG2 → the transfer gate TG3 at the time of the forward reading, and the transfer gate TG3 → the transfer gate TG2 → the transfer gate TG1 at the time of the backward reading.
Then, the transfer direction is controlled by switching the operation order (forward direction: solid arrow, reverse direction: broken arrow).

Here, the horizontal CCD shift register 2005 is used.
a to d are two-phase driving. Φ as is commonly known
The two types of registers 1 and φ2 are alternately connected. By alternately inputting pulses to the two types of registers, the potential of the CCD register changes, and charges are sequentially transferred in the direction of the output amplifier.

The above-described transfer gates TG1 to TG
Transfer between the three registers is performed by two types of registers (φ1, φ1
It is assumed that the processing is performed using the register of φ1 in 2).

Signals 2218 and 2219 are switch gate signals SW1 and SW2 for controlling the charge transfer direction. Although not shown, the above-described shift gates SH1 to SH
7. The switching of the transfer direction of the transfer gates TG1 to TG3 is performed by the switch gate signal SW1 (221).
8), performed in synchronization with SW2 (2219). Also,
The analog switches 2106a to 2106d are also switched in synchronization with the switch gate signals SW1 (2218) and SW2 (2219).

The analog switches 2106 a to 2106 d transfer the transfer register 200 when reading in the forward direction (in the direction of the solid arrow).
At the time of reading the output of 7a-d in the reverse direction (in the direction of the dashed arrow)
Select the output of the transfer registers 2004a to 2004d.

As is clear from the above description,
When reading in the forward direction, the output amplifiers 2102a to 2102d output red signals, the output amplifiers 2103a to 2103d output blue signals, and the output amplifiers 2104a to 2104d output green signals.
When reading in the reverse direction, the output amplifiers 2101a to 2101a to
d outputs a red signal, output amplifiers 2102a-d output blue signals, and output amplifiers 2103a-d output green signals.

FIG. 3 is a circuit block diagram of the signal processing circuit. The CCD linear image sensor 1100 is driven by a driver 3008. Driver 300
8 is supplied with power from the driver power supply 3011,
The driver power supply 3011 is controlled by the controller 3010.

The power supply to the CCD linear image sensor 1100 is supplied from a CCD power supply 3012, which is also controlled by the controller 3010.

The four signals for each color output from the CCD linear image sensor 1100 are adjusted to a predetermined level by a sample-and-hold circuit and a gain control amplifier in the analog signal processing unit 3001, and then adjusted in the analog signal processing unit 3001. The data is converted into digital data by an AD converter.

Here, the CCD linear image sensor 11
The output signals from 00 are different color signals depending on the reading direction as described above.

In the analog signal processing unit 3001, the amplifier gain and the reference level (offset) of the AD converter are switched according to the reading direction.

In the present embodiment, the resolution of the AD converter is described as 8 bits, but the invention is not limited to this.

The 96-bit digital data output from the analog signal processor 3001 is supplied to the CCD pixel array corrector 3002.

As described with reference to FIG. 2, in the CCD linear image sensor 1100, the linear photodiode array is divided into right and left, and the respective outputs are read in opposite directions. Output.

The CCD pixel array correction unit 3002 corrects this array according to the image processing circuit algorithm at the subsequent stage, and comprises a FIFO, a LIFO memory, and a logic circuit.

The line-to-line distance correction unit 3003 corrects the difference in the position of the line sensor for each color of the CCD linear image sensor 1100.

The shading correction unit 3004 corrects the sensitivity variation of each pixel of the CCD linear image sensor 1100, and has two types of correction data according to the reading direction (forward / reverse). This is because the CCD linear image sensor 1100 has a different charge transfer path in the reading direction (forward / reverse).

The masking correction unit 3005 corrects the RGB color space, and performs two corrections in the reading direction (forward / reverse).
With different types of correction coefficients, the output is constant for the color regardless of the reading direction.

The digital data normalized by the processing from the analog signal processing circuit 3001 to the masking correction unit 3005 is subjected to processing such as scaling and γ correction by the image processing unit 3006 using the page memory 3007.

In the above-described circuit configuration, for example, the setting and control of the gain and offset of the analog signal processing unit 3001, the memory control of the CCD pixel array correction unit 3002 and the inter-line distance correction unit 3003, and the correction coefficient of the masking correction unit 3005 are performed. The controller 3010 manages it.

The timing pulse necessary for each block is generated by the timing generator 3009, and the driving pattern of the CCD linear image sensor 1100 is changed via the driver 3008 by the CCD linear image sensor 1110.
00 is supplied.

In particular, CC supplied to driver 3008
For the D drive pulse, the controller 3010 performs duty control by ON / OFF control of the pulse.

FIG. 4 shows an example of the correspondence between one main scanning image stored in the page memory 3007 and the memory address (b) in the main scanning direction.

Since the detection signal of the CCD linear image sensor 1100 is divided right and left from the center and read out via the left and right output amplifiers, as shown in FIG. A dark current noise peak occurs.

Assuming that the number of effective pixels is 8800 pixels, addresses 0 to 8799 are assigned to one line in the main scanning. The average signal level D is the signal level of 800 pixels from addresses 4000 to 4799. Is calculated based on

While the signal level is quantized by 8 bits, the calculation of the average value is performed with higher precision. Here, for example, it is assumed that the processing is performed with 10-bit accuracy. This is because the change in the dark current noise distribution is more accurately captured, and the effect on the image quality is kept within 1 LSB.

As means for calculating the average, there is a means in which the controller 3010 reads data corresponding to a predetermined address in the page memory 3007 and calculates an average value based on the data. However, the means is not limited to this, and may be realized by an ASIC.

FIG. 5A shows the dark current noise distribution of the CCD linear image sensor 1100 in three states, that is, power supply is excessive, reference, and power shortage. As shown in the figure, the difference appears remarkably at both ends.

The optical black reference OB section is laid out at both ends of the CCD linear image sensor 1100, and the fluctuation of the signal level of the OB section and the fluctuation of the conversion range of the AD converter when the OB section is clamped. FIG. 5 (b) shows the correspondence.

Since the offset is adjusted by the clamp so that the average value in the OB period becomes the level (10) h, the signal level in the effective pixel period relatively fluctuates.

When the power supply is excessive, the effective pixel period signal level becomes lower than the level D0 in the reference state, and when the power supply is insufficient, the signal level becomes higher than the level in the reference state.

The controller detects the level fluctuation of the average value D accompanying the fluctuation of the signal level.

The average value D is D <D0−
If it is 0.25 LSB, the controller 3010 determines that the power is
11, the voltage of the CCD power supply 3012, the duty of the intermittent driving of the CCD driving pulse of the timing generation unit 3009, or the like, alone or in combination.
The control is performed in a direction to reduce the power supply to 00.

The average value D is D> D0 + with respect to the reference value D0.
If it is 0.25 LSB, the controller 3010 determines that the power supply is currently insufficient, and
The operation of increasing the voltage of the CCD power supply 3012, and controlling the duty of intermittent driving of the CCD driving pulse of the timing generation unit 3009 alone or in combination with the CCD linear image sensor 11
The control is performed in the direction of increasing the power supply to 00.

FIG. 6 shows an example of intermittent driving of the CCD driving pulse. In FIG. 6A, the reading time for one sheet is 1
Assuming that the non-reading time between documents and
The total reading time when reading 0 documents is (1 + 0.5) × 200 = 300 seconds = 5 minutes.

FIG. 6B shows a change in the average value D. The average value D falls below the reference D0-0.25 LSB at the 50th sheet. At this time, the controller 3010 determines that the power supply is excessive and starts intermittent driving of the CCD driving pulse (FIG. 6).
(C)).

In the intermittent driving, as shown in the enlarged view of FIG. 6A, the driving pulse is stopped between the originals, so that the power supplied from the driver can be suppressed to about 2/3 on average in the time direction. .

If the difference between the average value D and the reference value D0 still does not decrease, control such as lowering the driving voltage to the driver and lowering the power supply voltage of the CCD is performed in addition to the control by the intermittent driving.

Next, the average value D is 10
It becomes equal to the reference value D0 on the 0th sheet, and becomes the reference D0 on the 150th sheet.
Exceeds +0.25 LSB.

At this time, the controller 3010 determines that the power supply is insufficient, and switches the CCD drive pulse to the normal drive.

If the difference between the average value D and the reference value D0 still does not decrease, in addition to the control by the normal driving, the driving voltage to the driver is increased, and the power supply voltage of the CCD is increased.
Such control is also performed.

In this embodiment, the method of controlling the average value D so as to be within a certain range has been described. However, instead of the average value D, a maximum value or a minimum value within a predetermined address range is used. Is also good.

In the present embodiment, a CCD line image sensor is used as an image sensor. However, in a case where another device such as a two-dimensional image sensor for reading a two-dimensional image is used as an image sensor, an optical black image sensor may be used. It is possible to suppress the noise fluctuation due to the temporal change of the part, suppress the fluctuation of the black level, and suppress the image quality deterioration.

In this embodiment, the case where the document is continuously read by using the document feeder has been described. However, even in the case where the document feeder is not used or the continuous reading is not performed, for example, when the manual feed is performed, the document reading signal is also read. By controlling the power varying means in accordance with the level and a calculation value based on the level, it is possible to suppress the occurrence of a change in the black level in the image reading signal.

In the case of a copying machine using the present image reading apparatus, a laser diode is driven by an image signal in which a black level does not fluctuate, and the laser beam is exposed on a photosensitive member. High quality copy paper can be obtained.

[0105]

A means for detecting a reading signal level of a document, a power consumption varying means for changing power consumption in an image sensor, and a means for controlling the power consumption varying means in accordance with the reading signal level of the document. So that the temperature fluctuation of the optical black part of the image sensor and the fluctuation of the dark current noise distribution are suppressed,
Suppress the fluctuation of the signal level of the optical black part,
Therefore, it is possible to obtain a high-quality image signal without fluctuation of the black level.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a scanner according to the present invention and a conventional example.

FIG. 2 is a configuration diagram of a CCD linear image sensor according to the present invention and a conventional example.

FIG. 3 is a circuit configuration diagram according to the present invention and a conventional example.

FIG. 4 is a diagram showing a correspondence between an image image for one scanning line in a page memory and a memory address in the present invention and a conventional example.

FIG. 5 is a diagram illustrating a change in a dark current noise distribution of a conventional CCD linear image sensor.

FIG. 6 is a diagram illustrating intermittent driving of a CCD driving pulse according to the present invention.

FIG. 7 is a configuration diagram of a CCD linear image sensor according to the present invention and a conventional example.

FIG. 8 is an equivalent circuit diagram of a CCD transfer register according to the present invention and a conventional example.

FIG. 9 is a diagram illustrating a power consumption distribution of a conventional CCD.

FIG. 10 is a diagram illustrating heat radiation of a CCD linear image sensor using a conventional outer peripheral device.

FIG. 11 is a diagram showing a change in dark current noise distribution of a conventional CCD.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 CCD linear image sensor 11 Photodiode 12 Shift gate 13 Transfer register 14 Output amplifier 15 Power supply terminal 40 Heat sink 1000 Scanner 1000a Scanner main body 1000b Document feeder 1001 Lens unit 1002 First reflection mirror 1003 Second reflection mirror 1004 Third reflection mirror 1005 Halogen lamp 1006 Input tray 1007 Pick-up roller 1008 Feed roller 1009 Drift platen glass 1010 Platen glass 1011 Discharge tray 1012 First mirror unit 1013 Second mirror unit 1014 Stepping motor 1015 Document 1100 CCD linear image sensor 2000 Color CCD linear image sensor 2001 red CCD linear image sensor 2002 Blue CCD linear image sensor 2003 Green CCD linear image sensor 2001a-c Linear photodiode array with red on-chip color filter 2002a-c Linear photodiode array with blue on-chip color filter 2003a -C Linear photodiode array with green on-chip color filter 2004a-d, 2005a-d, 2006a-d, 2
007a-d CCD shift registers 2101a-d, 2102a-d, 2103a-d, 2
104a-d Output amplifiers 2106a-d Analog switches 2200-2202, 2215-2217 Transfer gates 2203, 2204, 2213, 2214 Switch gates 2205-2221 Shift gates 3001 Analog signal processing unit 3002 CCD pixel array correction unit 3003 Line distance correction unit 3004 shading correction unit 3005 masking correction unit 3006 image processing unit 3007 page memory 3008 CCD driver 3009 timing generation unit 3010 controller 3011 driver power supply 3012 CCD power supply

Claims (6)

[Claims] 1. An image reading apparatus for reading an image using an image sensor, comprising: means for detecting an image reading signal level; and power consumption varying means for changing power consumption in the image sensor. Image reading device. 2. The image reading apparatus according to claim 1, further comprising control means for controlling said power consumption varying means in accordance with a read signal level of said document. 3. The image reading device according to claim 1, wherein the power consumption varying means changes a power supply voltage to the image sensor. 4. The image reading apparatus according to claim 1, wherein the power consumption varying means changes a voltage of a driving power supply to a driver for driving the image sensor. 5. The image reading apparatus according to claim 1, wherein the power consumption varying means changes a duty of a driving power supply to a driver for driving the image sensor. 6. A copying machine using the image reading apparatus according to claim 1.