JPH06113137A - Image forming device - Google Patents

Abstract

PURPOSE:To stably adjust gain of a gain control circuit which is made into LSI on digital copying devices provided with scanners. CONSTITUTION:An A/D conversion output of an analog signal processing circuit 10 for digitalizing an analog signal from a CCD line sensor 5 at the time of reading a white reference board is outputted to CPU through a buffer 30b in a picture signal control circuit 30. CPU decides the optimum gain from the output and a present gain set value, and it is inputted to LSI 10 through a buffer 30c. Thus, the gain can stably be controlled by adjusting the input level of the analog signal which is to be A/D-converted from the outside of LSI 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image of a digital copying machine provided with an integrated circuit device useful as an element for image signal processing, for example, which outputs an output of a CCD line sensor and outputs normalized image data. Forming apparatus

[0002]

2. Description of the Related Art Recently, a CCD line sensor has been widely used as a photoelectric conversion element of an image reading apparatus. Various improvements have been made to this type of CCD line sensor, and with the advent of large CCD line sensors, they are now being used in image forming apparatuses such as facsimile machines and digital copying machines.

In the image forming apparatus described above, signal processing of the output of the CCD line sensor is becoming more important due to demands for higher speed, higher image quality, and colorization. Therefore, various large-scale integrated circuit devices (LSIs) are being developed to realize such high-level signal processing.

However, in the conventional LSI,
The input level of the analog signal input to this must be adjusted by using an external variable resistor or the like.

That is, the input voltage to the A / D converter for converting the output signal from the CCD line sensor into a digital value needs to be constant, and this has been manually adjusted. Therefore, adjustment time is required for each device,
In addition, there is a drawback in that adjustments between devices are likely to vary due to lack of accuracy.

[0006]

As described above, in the prior art, the input level of the analog signal to the A / D converter must be adjusted by using an external variable resistor or the like. However, there is a drawback in that the adjustment tends to vary.

Therefore, an object of the present invention is to provide an image forming apparatus capable of automating the gain adjustment of an analog signal and stabilizing the adjustment.

[0008]

To achieve the above object, in an image forming apparatus of the present invention, a photoelectric conversion element on which an optical image corresponding to an original image is formed, and this photoelectric conversion element. Generating means for generating a reference signal level for the output signal from the device, sample-holding means for sample-holding the signal output from the generating means, adjusting means for adjusting the gain of the signal sample-held by the sample-holding means, An amplifying means for amplifying the signal adjusted by the adjusting means, and a converting means for analog / digital converting the signal amplified by the amplifying means,
An integrated circuit device having the generating means, the sample-hold means, the adjusting means, the amplifying means, and the converting means as one-chip circuit elements and having an output terminal for taking out the output signal of the converting means to the outside. The adjustment is controlled according to the output of the photoelectric conversion element by controlling the adjusting means using the analog / digital converted signal output from the converting means via the output terminal of the integrated circuit device. The control unit controls the gain adjustment by means, and the image forming unit forms the original image on the image forming medium based on the output signal from the integrated circuit device.

Further, in the image forming apparatus of the present invention, a scanning means for optically scanning the original to obtain an optical image corresponding to the image of the original, and an optical image obtained by the scanning by the scanning means are provided. A photoelectric conversion element that performs photoelectric conversion, a detection unit that detects the DC potential of the invalid pixel section of this photoelectric conversion element as a reference signal level, and the reference signal detected by this detection unit, from the effective pixel section of the photoelectric conversion element. Means for clamping the output signal of the device, sample-hold means for sampling and holding the output signal from the clamp means, variable gain amplifier adjusting means for varying the gain of the output signal from the sample-holding means, and the variable gain amplifier adjusting means. The analog / digital conversion means for analog / digital converting the output signal from the And an integrated circuit device having an output terminal for taking out the output signal from the analog / digital conversion means to the outside, and the analog / digital conversion output via the output terminal of the integrated circuit device. Control means for controlling the gain adjustment of the variable gain amplifier adjusting means from outside the chip based on the output signal from the means, and the integrated circuit in which the gain adjustment of the variable gain amplifier adjusting means is performed by the control means. Processing means for obtaining a read signal corresponding to the original image by performing various kinds of image processing on an output signal from the apparatus; and a latent image forming means for forming a latent image according to the read signal from the processing means,
It is composed of a developing means for developing the latent image formed by the latent image forming means, and an image forming means for forming the developer image visualized by the developing means on the image forming medium. .

[0010]

According to the present invention, since the gain control can be performed easily and accurately by the above-mentioned means, it is possible to suppress the variation in the adjustment between the devices.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a digital copying apparatus according to the present invention.

That is, this digital copying apparatus comprises, for example, a scanner 41 as an image reading apparatus and a printer 43 as an image forming apparatus.

The scanner 41 comprises a first carriage 221 and a second carriage 22 which are movable in the direction of arrow B in the figure.
2, an image forming lens 227, a CCD line sensor 5 as a photoelectric conversion element, and a control board 229 for electrically / mechanically controlling these.

In FIG. 1, the original OG is an original table glass 2
The document OG is placed downward on the table 20, and the center of the document OG is placed on the front right side of the document table glass 220 in the lateral direction. The original OG is pressed on the original table glass 220 by an original fixing cover 212 which is provided so as to be openable and closable.

The original OG is illuminated by a fluorescent lamp (light source) 223, and its reflected light is reflected by mirrors 224, 225, and 2.
26 and the imaging lens 227, the light is focused on the surface of the CCD line sensor 5 having a plurality of light receiving elements arranged in a row.

A white reference plate 215 is provided in the vicinity of the platen glass 220 described above.

Here, the mirror 224, the fluorescent lamp 223, a light quantity sensor (light quantity detection circuit) (not shown) for detecting the quantity of light, and a heat retaining heater for keeping the temperature of the fluorescent lamp 223 constant are provided. 1 carriage 221,
The second carriage 222 including the mirrors 225 and 226 is configured to move at a relative speed of 2: 1 so that the optical path length is constant.

First carriage 221 and second carriage 2
Reference numeral 22 is moved from right to left by a pulse motor (not shown) as a stepping motor in synchronization with the read timing signal, and performs sub-scanning.

The sub-scanning speed is 2 depending on the reading magnification.
The excitation method of the phase pulse motor is switched by 1/2 phase excitation and micro step drive. Particularly, in the low speed region, the pulse motor driver (not shown) is configured so that the current waveform that cancels the natural vibration of the drive system is input to the pulse motor.

As described above, the images of the original OG placed on the original table glass 220 are sequentially read line by line, and the control board 229 indicates the density of the image.
It is output as bit digital image data.

The printer 43 includes a laser optical system 240,
The image forming unit 239 is a combination of electrophotographic systems capable of forming an image on a transfer paper (image forming medium) P, and a control board 243 for controlling the driving of these.

That is, the image data read from the original OG by the scanner 41 is the control board 2
It is synchronized by an image processing circuit (not shown) on 43 and converted into laser light from the semiconductor laser oscillator 241.

The output laser light is shaped by a beam shaping optical system including, for example, a cylindrical lens, and is deflected by a polyhedral rotating mirror 242 which is rotationally driven by a high speed rotation motor using an air bearing.

The deflected laser light is reflected by a mirror 244 through an fθ lens (not shown). Then, an image is formed as a spot having a necessary resolution at the exposure position 246A on the photoconductor drum 246, and scanning exposure is performed. As a result, a latent image corresponding to the image data is formed on the photosensitive drum 246.

The deflected laser light is synchronized by being detected by a beam detector (not shown) composed of a photodiode.

Around the photosensitive drum 246, a charger 247 for charging the drum surface and a developing device 24 are provided.
8, a transfer charger 249, a peeling charger 250, a cleaner 251 and the like are provided.

The photosensitive drum 246 has a drum surface rotatably driven at a peripheral speed of V0 by a drive motor (not shown), and is provided with a charging charger provided opposite to the photosensitive drum surface having a grid electrode. It is charged by 247.

The laser light is spot-imaged at the exposure position 246A on the charged photosensitive drum 246,
As a result, the photosensitive drum 246 on which the latent image is formed is rotated at the speed V0 to the developing position. Then, at this position, the latent image on the photosensitive drum 246 is developed by the toner from the developing device 248.

Photosensitive drum 246 on which a toner image is formed
Are still rotated at V0. Then, the toner image on the photoconductor drum 246 is transferred by the transfer charger 249 onto the transfer paper P that is timely supplied by the paper feeding system at the transfer position.

Here, the above-mentioned paper feeding system is constituted by means capable of selectively feeding the transfer paper P from the cassette 252, for example.

That is, the transfer paper P in the cassette 252 is selectively separated and fed one by one by, for example, the paper feed roller 253 and the separation roller 254.
Then, it is fed to the registration roller 255 and fed to the transfer portion (transfer position) at a predetermined timing.

Further, on the downstream side of the transfer charger 249, there are provided a paper transport mechanism 256, a fixing device 257, a paper discharge roller 258 for discharging the image-formed transfer paper P to the outside of the machine, and a paper discharge tray 259. Has been done.

As a result, the transfer paper P having the toner image fixed by the fixing device 257 is ejected to the paper ejection tray 259 via the paper ejection roller 258.

Further, the photosensitive drum 246 which has finished the transfer onto the transfer paper P is returned to the initial state by removing the residual toner and the like by the cleaner 251, that is, it stands by for the next image formation.

Next, the operation of the above digital copying machine will be described.

For example, it is assumed that the original OG is set on the original platen glass 220 and the operator gives an instruction to start the operation. Then, first, the control board 2
In response to an instruction from 29, a stepping motor or the like (not shown) is operated, and the document image is read by the scanner 41.

That is, the first carriage 221 and the second carriage 222 are moved at a predetermined speed on the lower surface of the original OG in the direction of arrow B in the figure, and the original OG is illuminated by the fluorescent lamp 223 during the sub-scanning. .

Then, the reflected light from the original OG is imaged on the CCD line sensor 5 via the mirrors 224, 225, 226 and the imaging lens 227, so that the light intensity of each line is adjusted. An analog electric signal (image signal) is output.

This electric signal is supplied to the control board 229, where it is subjected to predetermined processing such as analog image processing, digital image processing, shading correction processing, and various image processing (details will be described later). As a result, it is generated as 8-bit digital image data indicating the contrast of the image.

Thus, the scanner 41 is read from the original OG.
When the image data is read by, the printer 43 forms an image according to an instruction from the control board 243.

That is, based on the above image data,
Laser light is generated from the semiconductor laser oscillator 241. Then, the laser light is deflected by the polyhedral rotating mirror 242, further reflected by the mirror 244, and imaged on the photosensitive drum 246.

This laser beam rotates in the direction of the arrow in the figure, and the drum surface uniformly charged by the charging charger 247 is scanned and exposed, whereby a latent image corresponding to the image data is formed on the photosensitive drum 246. Is formed.

The latent image formed on the photosensitive drum 246 is developed by the toner from the developing device 248 and sent to the transfer position.

Then, the transfer sheet P is fed from the cassette 252 at the same timing as the transfer of the toner image to the transfer position, so that the toner image on the photosensitive drum 246 is transferred by the action of the transfer charger 249. Paper P
Transcribed on.

After that, the transfer paper P is separated by the peeling charger 25.
By the action of 0, the toner image is peeled off from the photoconductor drum 246, conveyed by the sheet conveying mechanism 256 and sent to the fixing device 257, where the toner image is fixed.

The transfer paper P that has passed through the fixing device 257 is discharged onto the paper discharge tray 259 by the paper discharge roller 258, whereby the series of image forming operations is completed.

By repeating such a process, the image reading device including the scanner 41 and the printer 43 are formed.
The image forming operation of the digital copying apparatus is performed by combining the image forming apparatus including the above.

FIG. 2 shows the configuration of the control board 229 arranged in the scanner 41.

That is, the control board 229 is provided with the analog signal processing circuit (image processing LSI) 10 and the image reading control section 20.

The image reading control section 20 includes a CPU 21 which controls the scanner 41 as a whole, a shading correction circuit 22, various image processing circuits 23, and an interface circuit 2.
4, ROM 25, working RAM (WORKING ·
RAM) 26, input / output circuits (I / O) 27, 28, 2
9 and the image signal control circuit 30 are connected via an address bus 31 and a data bus 32.

The shading correction circuit 22 has a black shading memory and a white shading memory each of which is composed of a RAM. The black shading data and the white shading data stored in the shading correction circuit 22 allow the digital image data from the analog signal processing circuit 10 to be output. To correct shading distortion such as high-frequency distortion due to bit-to-bit variation of the CCD line sensor 5 and low-frequency distortion of the optical system.

The various image processing circuits 23 perform image processing such as γ correction and edge enhancement on the digital image data whose shading distortion has been corrected by the shading correction circuit 22.

The interface circuit 24 outputs the image data output from the various image processing circuits 23 to the external peripheral device 1 such as the host computer or the printer 43. In addition, this interface circuit 24
Receives the operation control command from the external peripheral device 1,
The status of the scanner 41 is returned as the status.

The ROM 25 stores a control program for operating the scanner 41, a data table, and the like.

The working RAM 26 is for storing control data and calculation data for temporary storage.

The I / O 27 exchanges information such as control signals and data signals between the CPU 21 and the analog signal processing circuit 10.

The I / O 28 functions as a motor control circuit for controlling the drive of the first and second carriages 221 and 222 between the CPU 21 and the pulse motor 2 as a carriage motor and the encoder 3. is there.

The I / O 29 functions as a lamp control circuit for controlling lighting, extinguishing, light amount, etc. of the fluorescent lamp 223 between the CPU 21 and the light source 223 as the fluorescent lamp and the light amount detection circuit 4. To do.

Next, the operation of the image reading control section 20 will be described.

For example, various setting commands such as a paper size setting command, a magnification setting command and a movement setting command from the external peripheral device 1 are received by the interface circuit 24 and then decoded by the CPU 21.

Then, the scanner 41 is operated by the CPU 21.
Is reset, and the state is returned to the external peripheral device 1 via the interface circuit 24 as a status.

Thus, the external peripheral device 1 can detect the state of the scanner 41 by receiving the status.

When the CPU 21 receives the document reading start command from the external peripheral device 1 through the interface circuit 24, the reading of the document OG by the scanner 41 is started.

First, the CPU 21 gives an instruction to the analog signal processing circuit 10 through the I / O 27 to set the inside thereof to a predetermined state (details will be described later).

Next, the CPU 21 causes the I / O 28
To the motor 2 and the encoder 3
The drive of the first and second carriages 221 and 222 is controlled by.

In this case, the mirror 224 has the white reference plate 215.
The first carriage 221 is moved so as to be located below.

Then, the CPU 21 causes the I / O 29
Is given, the surface image of the white reference plate 215 is imaged on the CCD line sensor 5 with the fluorescent lamp 223 turned off, and the reading is performed.

The image data read by the CCD line sensor 5 is stored in the black shading memory in the shading correction circuit 22 as black shading data.

This black shading data is the CC
It is used as correction data for removing the inherent dark level noise of the D line sensor 5.

When the black shading data has been read, the CPU 21 causes the I / O 28 and I / O 2 to be read.
Instructions are given to 9.

That is, while the first carriage 221 is moved under the white reference plate 215 by the motor 2 and the encoder 3, the fluorescent lamp 223 is turned on, so that the surface image of the white reference plate 215 is read by the CCD line sensor. The image is formed at 5, and the reading is performed.

The image data read by the CCD line sensor 5 is stored in the white shading memory in the shading correction circuit 22 as white shading data.

This white shading data is the CC
It is used as correction data for removing light level noise (high frequency noise) peculiar to the D line sensor 5 and low frequency distortion due to an optical system such as the fluorescent lamp 223 and the imaging lens 227.

It should be noted that, for some reason, the first carriage 2
When 21 cannot be moved below the white reference plate 215 within a predetermined time, the CPU 21 shifts to an error operation and transmits a code signal corresponding to a carriage operation error as a status from the interface circuit 24 to the external peripheral device 1. It is supposed to do.

On the other hand, when the reading of the white shading data is completed, the first carriage 221 is moved to the position below the original platen glass 220 and stopped while the fluorescent lamp 223 remains lit.

As a result, the scanner 41 waits for the VSYNC command from the external peripheral device 1.

In this state, when the CPU 21 receives the VSYNC command from the external peripheral device 1 via the interface circuit 24, the reading scanning of the original OG is started.

That is, the CPU 21 causes the I / O 2
8 is instructed, and the drive of the first and second carriages 221 and 222 is controlled by the motor 2 and the encoder 3.

In this case, when the number of rotations according to the already set magnification is reached, the first and second carriages 221 and
222 is switched to a constant speed operation, and is moved under the platen glass 220 at a predetermined speed.

While the first and second carriages 221 and 222 scan the original OG at a constant speed, the CCD line sensor 5 is
Horizontal sync signal (CCD from the image signal control circuit 30)
Controlled by the light accumulation time for driving the line sensor, the formed optical signal is converted into an analog image signal and sent to the analog signal processing circuit 10.

The analog image signal is subjected to gain amplification and A / D conversion by the analog signal processing circuit 10 and then sent to the shading correction circuit 22 as digital image data.

The shading correction circuit 22
At, the shading distortion is corrected by the black shading data and the white shading data.

The digital image data whose shading distortion has been corrected is subjected to image processing such as γ correction and edge enhancement which have already been set in the various image processing circuits 23, and reproducibility of the original image is ensured.

That is, when the image data read by the CCD line sensor 5 is reproduced by the external peripheral device 1, that is, when the printer 43 forms an image, a reproduced image close to the original image can be output.

The image data subjected to such processing is output to the external peripheral device 1 through the interface circuit 24, and is used for the above-mentioned image forming operation by the printer 43, for example.

Regarding the reading area of the original OG, the CCD
By simultaneously performing the operation in the main scanning direction with respect to the longitudinal direction of the line sensor 5 and the operation in the sub scanning direction with respect to the moving direction of the carriages 221 and 222, the image information on the original OG can be continuously read.

Now, when the reading of the original OG is completed,
The CPU 21 gives an instruction to the I / O 28, and the motor 2 and the encoder 3 control the driving of the first and second carriages 221 and 222.

In this case, the first and second carriages 22 are
1, 222 are moved at a high speed in the direction opposite to the reading, and are returned to the initial position.

Then, by returning to the initial position, the CPU
A stop instruction is given to the I / O 28 by 21 and the driving of the first and second carriages 221 and 222 is stopped.

That is, when the CPU 21 receives a read end command from the external peripheral device 1 via the interface circuit 24, the first carriage 2
21 is stopped near the white reference plate 215.

The CPU 21 gives an instruction to the I / O 29 to turn off the fluorescent lamp 223.

When the next command is received from the external peripheral device 1, the scanner 41 becomes ready (waiting for a new instruction).

In the case of shifting to the continuous reading operation, in the state where the first and second carriages 221 and 222 are returned to the initial positions, the state of waiting for the VSYNC command from the external peripheral device 1 is continued, and the CPU 21 Is V
The operation described above is repeated by re-receiving the SYNC command.

FIG. 3 shows a schematic configuration of the image signal control circuit 30 described above.

That is, the image signal control circuit 30
It is composed of buffers 30a, 30b, 30c, various timing generation circuits 30d, and a decoder circuit 30e.

The buffer 30a converts the output signal from the A / D converter (ADC109 in FIG. 6) in the analog signal processing circuit 10 into the shading correction circuit 22 in the image reading control unit 20 and the clamp circuit (see FIG. 6 for output to a DC signal component calculation / removal circuit (not shown) for fine adjustment of the clamp 101).

The buffer 30b outputs an output signal from the A / D converter in the analog signal processing circuit 10 to an external control circuit such as the CPU 21 in the image reading control section 20 via a peak detection circuit (not shown). To output to.

The buffer 30c is for introducing into the analog signal processing circuit 10 the mode and the gain setting signal supplied from the external control circuit such as the CPU 21 via the data bus 32.

The various timing generation circuits 30d have the above-mentioned C
A horizontal synchronizing signal for driving the CD line sensor 5,
The timing signal for controlling the operation of the analog signal processing circuit 10 is generated.

The decoder circuit 30e inputs the address signal, the write signal WT or the read signal RD supplied from the external control circuit such as the CPU 21 via the address bus 31, and controls the input / output of the buffers 30b and 30c. It is for generating a signal.

FIG. 4 shows the configuration of the CCD line sensor (photoelectric conversion element) 5 described above.

That is, this CCD line sensor 5 is
A photodiode array 5 ₁ is provided in the center, and storage electrodes 5 ₂ and 5 ₂ , shift gates 5 ₃ and 5 ₃ and CCD analog shift registers 5 ₄ and 5 ₄ are provided on both sides of the photodiode array 5 _1. Has been done.

[0104] The photodiode array 5 _1, element of the central portion (photodiode) S1～S2592 is used as image signals, before and after the element D13～D64, D
65 to D92 are for dummy.

The magnification of the optical system is determined so that the total length of the image signal elements S1 to S2592 matches the main scanning width.

Of the dummy devices D13 to D64, the light receiving surface of the photodiodes of the devices D13 to D29 is provided with an aluminum vapor deposition film to block light, and a reference bit (for creating a reference voltage of the sensor output ( (Black reference pixel)
Has become.

In addition, the CCD line sensor 5 is constructed by providing necessary input / output section, power source and the like and wiring.

FIG. 5 shows a signal waveform in each part of the CCD line sensor 5.

That is, the shift gates 5 ₃ and 5 ₃ have
A gate signal 5a shown in FIG. 9A (1 cycle is a main scanning cycle, and τ _INT is an optical signal storage time) is added.

CCD analog shift registers 5 ₄ , 5 ₄
, Clock signals 5b and 5c for driving the same are added, respectively, as shown in FIGS.

The reset signal 5d shown in FIG.
Is to initialize the voltage of the floating capacitor in the output stage by being applied to the output gate so that the sensor output correctly corresponds to the pixel data transferred by the shift registers 5 ₄ and 5 ₄ .

CCD analog shift register 5 described above
The pulses of the clock signals 5b and 5c of ₄ and 5 ₄ and the reset signal 5d are assigned in time series corresponding to the respective elements of the photodiode array 5 ₁ shown in FIG.

Further, the sensor output 5e shown in FIG.
Is output from the output terminal, and the output voltage (dark output voltage) V during the dummy output reference bit period
y becomes a reference voltage when the sensor 5 is dark, and each pixel data (effective output voltage) is output from the voltage Vy by ΔVx according to the amount of light incident on the photoelectric conversion element.

FIG. 6 shows a configuration of an analog signal processing circuit 10 which can be replaced as the above image processing LSI.

That is, the clamp circuit 101 that processes the output from the CCD line sensor 5, the sample hold circuit 102, the gain control circuit 103, the amplification circuit (buffer) 108 that amplifies the output from the gain control circuit 103, and this amplification. It is configured by an ADC 109 that converts the analog output of the circuit 108 into a digital value.

The clamp circuit 101 sets the voltage Vy in the reference bit period from the sensor output 5e shown in FIG. 5 (e) to a certain reference level, and its operation is controlled by the timing signal 101a. ing.

The sample hold circuit 102 samples and holds the output of the clamp circuit 101.
The operation is controlled by the timing signal 102a.

The gain control circuit 103 is for adjusting the gain of the output of the sample hold circuit 102, and its attenuation amount is controlled by the control signals 103a and 103b from the external control circuit such as the CPU 21. There is.

That is, since the amplification factor of the amplifier circuit 108 is a constant value, if the value of the analog signal (sensor output 5e) input to the LSI 10 is too large, it may exceed the reference voltage of the ADC 109 when amplified. In such a case, malfunction occurs.

In order to prevent this, the gain control circuit 103 adjusts the gain of the analog signal.

FIG. 7 shows the relationship between the control signal and the amount of attenuation in the gain control circuit 103.

Here, 1 bit as an enable signal is assigned to the control signal 103a, and signals Sg1 and Sg0 for 2 bits are assigned to the control signal 103b.

In the case of this embodiment, when the enable signal is "1", the attenuation amount is "0" regardless of the states of the signals Sg1 and Sg0.

The enable signal and the signal Sg1,
When both Sg0 are "0", the attenuation amount is "0".

Furthermore, when the enable signal is "0" and the signals Sg1 and Sg0 are "0, 1", the attenuation amount is "2" and the signals Sg1 and Sg0 are "1, 0".
In the case of, it becomes "4", and in the case of "1,1", it becomes "6".

By adding the number of signals Sgn (n = 0, 1), more precise control or a large amount of attenuation (amplification) can be handled.

Here, the gain setting operation in the above configuration will be described.

In FIG. 8, first, the first carriage 22
1 corresponds to the white reference plate 215, and the fluorescent lamp 223 is turned on in this state (step ST1). Then, the white reference plate 21 illuminated by the lighting of the fluorescent lamp 223.
The reflected light from 5 is imaged on the CCD line sensor 5 via the optical system such as the imaging lens 227 (step S).
T2).

As a result, the CCD line sensor 5 outputs the sensor output 5e as shown in FIG. 5 (e), which is input to the LSI 10 as an analog signal.

The analog signal input to the LSI 10, that is, the white reference signal, is sent to the ADC 109 via the clamp circuit 101, the sample hold circuit 102, the gain control circuit 103, and the amplification circuit 108, where it is converted into a digital value. (Step ST3).

The output of the ADC 109 is sent to the image reading control section 20 via the image signal control circuit 30.
It is sent to an external control circuit such as the upper CPU 21 (step ST4) and used for calculation of a gain that optimizes the input level of the analog signal to the ADC 109 (step S).
T5).

That is, the digital white reference signal from the ADC 109 is output from the peak detection circuit (not shown) in the image signal control circuit 30 onto the data bus 32 via the buffer 30b, and the image reading control unit 20 is read. Upper C
It is sent to an external control circuit such as the PU 21.

As a result, in the external control circuit such as the CPU 21, the gain setting value currently set and the ADC 1
Based on the 09 output (digital white reference signal), AD
The amount of attenuation that optimizes the gain of the analog signal input to C109 is determined.

Then, the control signals 103a,
103b is output from the data bus 32 to the gain control circuit 103 in the LSI 10 via the buffer 30c in the image signal control circuit 30 (step ST6).

As a result, the analog input range can be widened, and the analog signal of the optimum level is always input to the ADC 109.

Thus, the gain control circuit 103
After the gain is determined, the movement of the first and second carriages 221 and 222 is started, so that the original OG set on the original platen glass 220 is read.

Therefore, the image signal for the original OG read by the CCD line sensor 5 is gain-adjusted by the gain control circuit 103 set to the optimum gain value, and then converted into digital image data by the ADC 109, Shading correction circuit 22 in the next stage
Will be sent to.

As described above, easy and accurate gain control can be performed.

That is, A / when reading the white reference plate
The optimum gain is determined from the D conversion output and the current gain setting value, and the gain of the gain control circuit implemented in the LSI can be automatically adjusted with this. This allows the input level of the analog signal to be A / D converted to be adjusted easily and accurately from the outside of the LSI, so that it is possible to suppress variations in the adjustment between the devices. Therefore, stable adjustment can be performed between each device, and reliable A / D
The conversion can be realized.

In the above embodiment, one LSI is used.
The case of the chip configuration has been described as an example, but the present invention is not limited to this, and it is also possible to use an LSI configured with two or more chips by functionally dividing it.

Further, not only when reading the white reference plate,
For example, instead of the white reference plate, scan the white background of the original,
Even if the gain control is performed based on that, the same effect can be obtained.

In addition, it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0143]

As described above in detail, according to the present invention, it is possible to provide an image forming apparatus capable of automating the gain adjustment of an analog signal and stabilizing the adjustment.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an outline of a digital copying apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a control board in the same manner.

FIG. 3 is a block diagram showing a configuration of an image signal control circuit, similarly.

[FIG. 4] Similarly, a CCD line sensor (photoelectric conversion element)
FIG.

FIG. 5 is a diagram similarly showing a signal waveform of the CCD line sensor.

FIG. 6 is likewise an analog signal processing circuit (image processing L
The block diagram which shows schematic structure of (SI).

FIG. 7 is a diagram for explaining the relationship between the control signal and the attenuation amount, similarly.

FIG. 8 is a flow chart similarly shown for explaining a gain setting operation.

[Explanation of symbols]

1 ... External peripheral device, 5 ... CCD line sensor (photoelectric conversion element), 10 ... Analog signal processing circuit (LS for image processing)
I), 20 ... Image reading control section, 21 ... CPU, 22 ... Shading correction circuit, 30 ... Image signal control circuit, 41
... Scanner, 43 ... Printer, 101 ... Clamp circuit,
Reference numeral 102 ... Sample hold circuit, 103 ... Gain control circuit, 109 ... ADC, 215 ... White reference plate, 22
0 ... Original platen glass, 221 ... First carriage, 222 ...
Second carriage, 223 ... Fluorescent lamp (light source), 22
4, 225, 226 ... Mirror, 229 ... Control board, 2
39 ... Image forming unit, 240 ... Laser optical system, 241 ... Semiconductor laser oscillator, 242 ... Polyhedral rotating mirror, 246 ... Photosensitive drum, 247 ... Charging charger, 248 ... Developing device, 249 ... Transfer charger, 252 ... Cassette, 25
7 ... Fixer.

Claims (2)

[Claims] 1. A photoelectric conversion element on which an optical image corresponding to an original image is formed, a generation means for generating a reference signal level with respect to an output signal from the photoelectric conversion element, and a signal output from this generation means. Sample-hold means for sample-holding, adjusting means for adjusting the gain of the signal sample-held by this sample-hold means, amplifying means for amplifying the signal adjusted by this adjusting means, and the signal amplified by this amplifying means An output for extracting the output signal of the converting means to the outside, comprising: An integrated circuit device having a terminal, and an output from the conversion means via the output terminal of the integrated circuit device. Control means for controlling the adjusting means by using the inputted analog / digital converted signal, thereby causing the adjusting means to perform gain adjustment according to the output of the photoelectric conversion element; and the integrated circuit device. And an image forming unit for forming the original image on the image forming medium based on an output signal from the image forming apparatus. 2. A scanning means for optically scanning an original to obtain an optical image corresponding to the image of the original, a photoelectric conversion element for photoelectrically converting the optical image obtained by scanning by the scanning means, and this photoelectric conversion. Detection means for detecting the DC potential of the invalid pixel portion of the element as a reference signal level, clamp means for clamping the output signal from the effective pixel portion of the photoelectric conversion element with the reference signal detected by the detection means, and this clamp Sample-hold means for sample-holding the output signal from the means, variable gain amplifier adjusting means for varying the gain of the output signal from the sample-hold means, and analog for analog / digital converting the output signal from the variable gain amplifier adjusting means / Digital conversion means
It is configured as a circuit element of one chip, and the analog /
An integrated circuit device having an output terminal for taking out an output signal from the digital conversion means to the outside, and an output signal from the analog / digital conversion means output via the output terminal of the integrated circuit device Based on the control means for controlling the gain adjustment of the variable gain amplifier adjusting means from outside the chip, the output signal from the integrated circuit device on which the gain adjustment of the variable gain amplifier adjusting means is performed by the control means is performed. A processing unit that obtains a read signal corresponding to the original image by performing various kinds of image processing, a latent image forming unit that forms a latent image according to the read signal from the processing unit, and the latent image forming unit. A developing means for visualizing the formed latent image; and an image forming means for forming the developer image visualized by the developing means on the image forming medium. That the image forming apparatus.