Image density correction device and image density correction method, and image reading device and image forming apparatus

Claim 2

An image density correction device, comprising: a photoelectric conversion element having first and second blocks, for photoelectrically converting received light; first means for obtaining an absolute value of an amplitude of each of first and second output signals output from the first block of the photoelectric conversion element; second means for comparing the absolute values with predetermined reference values to obtain differences thereof; first correction means for correcting the first and second output signals on the basis of the differences obtained by the second means; and second correction means for correcting third and fourth output signals from the second block on the basis of the differences obtained by the second means.

Claim 3

An image density correction device according to claim 1 , wherein the photoelectric conversion element outputs first and second output signals from the first block, and outputs third and fourth output signals from the second block.

Claim 4

An image density correction device according to claim 1 , wherein the first means includes first differential amplifying circuits for dividing the first and second output signals from the first block into image signals and control signals, terminal-based detection circuits for detecting amplitude voltages of the first and second output signals from the control signals obtained by the first differential amplifying circuits, and second differential amplifying circuits for detecting an absolute value of an amplitude of the first and second output signals on the basis of the amplitude voltages detected by the terminal-based detection circuits.

Claim 5

An image density correction device according to claim 1 , wherein the second means comprises comparison circuits for comparing the absolute values obtained by the first means with the predetermined reference values to obtain the differences thereof.

Claim 6

An image density correction device according to claim 1 , wherein the first and second correction means include dividing means for dividing the plurality of output signals output from the photoelectric conversion element into image signals and control signals, first detection means for detecting amplitude voltages of the plurality of output signals from the control signals obtained by the dividing means, second detection means for detecting absolute values of an amplitude of the plurality of output signals on the basis of the amplitude voltage detected by the first detection means, comparison means for comparing the absolute amplitude voltage values obtained by the second detection means with the predetermined reference values to obtain error signal voltages, voltage holding means for holding the error signal voltages output from the comparison means, conversion means for converting the voltages held by the voltage holding means into electric currents, and correction means for correcting the image signals divided from the plurality of output signals of the photoelectric conversion element by the dividing means so as to have voltage of predetermined values with use of the electric currents converted from the voltages by the conversion means.

Claim 7

An image density correction method by which an output signal of a photoelectric conversion element receiving reflection light from an irradiated document is corrected, wherein the output signal of the photoelectric conversion element is divided into an image signal and a control signal, an amplitude voltage of the output signal is detected from the obtained control signal, an absolute value of an amplitude of the output signal is detected on the basis of the detected amplitude voltage, the obtained absolute value is compared with a predetermined reference value to obtain an error signal voltage, the obtained error signal voltage is held, the held voltage is converted into an electric current, and the image signal divided from the output signal of the photoelectric conversion element is corrected to have a predetermined voltage with use of the electric current converted from the held voltage.

Claim 8

An image density correction method by which an output signal of a photoelectric conversion element receiving reflection light from an irradiated document is corrected, wherein the output signal of the photoelectric conversion element is divided into an image signal and a control signal, an amplitude voltage of the output signal is detected from the obtained control signal, an absolute value of an amplitude of the output signal is detected on the basis of the detected amplitude voltage, the obtained absolute value is compared with a predetermined reference value to obtain an error signal voltage, the obtained error signal voltage is held, the held voltage is converted into an electric current, and the image signal divided from the output signal of the photoelectric conversion element is corrected to have a predetermined voltage with use of the electric current converted from the held voltage.

Claim 9

An image reading device which irradiates a document and reads an image of the document with use of a photoelectric conversion element having first and second blocks and photoelectrically converting received light reflected from the document by correcting an output signal from the photoelectric conversion element, comprising: first means for obtaining an absolute value of an amplitude of each of first and second output signals output from the first block of the photoelectric conversion element; second means for comparing the absolute values with predetermined reference values to obtain differences thereof; first correction means for correcting the first and second output signals on the basis of the differences obtained by the second means; second correction means for correcting third and fourth output signals output from the second block on the basis of the differences obtained by the second means; transfer means for receiving the first and second output signals corrected by the first correction means and the third and fourth output signals corrected by the second correction means, and correcting a pixel arrangement of the output signals, thereby obtaining an original output signal, and then outputting the original output signal; and processing means for processing the original output signal which is output from the transfer means and has the original pixel arrangement.

Claim 10

An image reading device which irradiates a document and reads an image of the document with use of a photoelectric conversion element having first and second blocks and photoelectrically converting received light reflected from the document by correcting an output signal from the photoelectric conversion element, comprising: first means for obtaining an absolute value of an amplitude of each of first and second output signals output from the first block of the photoelectric conversion element; second means for comparing the absolute values with predetermined reference values to obtain differences thereof; first correction means for correcting the first and second output signals on the basis of the differences obtained by the second means; second correction means for correcting third and fourth output signals output from the second block on the basis of the differences obtained by the second means; transfer means for receiving the first and second output signals corrected by the first correction means and the third and fourth output signals corrected by the second correction means, and correcting a pixel arrangement of the output signals, thereby obtaining an original output signal, and then outputting the original output signal; and processing means for processing the original output signal which is output from the transfer means and has the original pixel arrangement.

Claim 11

An image reading device which irradiates a document and reads an image of the document with use of a quadruplex photoelectric conversion element for dividing image data into four groups and photoelectrically converting received light reflected from the document by correcting first, second, third, and fourth output signals from the quadruplex photoelectric conversion element, comprising: first correction means for dividing the first output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with a predetermined reference value, and correcting the divided image signal to have a predetermined voltage with use of an error signal obtained by the comparison; second correction means for dividing the second output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction means; third correction means for dividing the third output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as the reference value from the first correction means; fourth correction means for dividing the fourth output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as the reference value from the first correction means; transfer means for transferring the image signal corrected by the first correction means, the image signal corrected by the second correction means, the image signal corrected by the third correction means, and the image signal corrected by the fourth correction means by which a pixel arrangements of the image signals are corrected to an original one; and processing means for processing the output signals which are transferred from the transfer means and have the original pixel arrangement.

Claim 12

An image reading device which irradiates a document and reads an image of the document with use of a quadruplex photoelectric conversion element for dividing image data into four groups and photoelectrically converting received light reflected from the document by correcting first, second, third, and fourth output signals from the quadruplex photoelectric conversion element, comprising: first correction means for dividing the first output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with a predetermined reference value, and correcting the divided image signal to have a predetermined voltage with use of an error signal obtained by the comparison; second correction means for dividing the second output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction means; third correction means for dividing the third output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as the reference value from the first correction means; fourth correction means for dividing the fourth output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as the reference value from the first correction means; transfer means for transferring the image signal corrected by the first correction means, the image signal corrected by the second correction means, the image signal corrected by the third correction means, and the image signal corrected by the fourth correction means by which a pixel arrangements of the image signals are corrected to an original one; and processing means for processing the output signals which are transferred from the transfer means and have the original pixel arrangement.

Claim 13

An image reading device according to claim 8 , wherein the quadruplex photoelectric conversion element receives the reflected light from four pixel groups obtained by dividing an entire image region of the document in a main scanning direction into an upper region and an lower region and further dividing all pixels in the image regions of the document into odd and even pixels.

Claim 14

An image forming apparatus which irradiates a document and forms an image of the document on the basis of a corrected signal output from a photoelectric conversion element having first and second blocks and photoelectrically converting received reflected light from the document, comprising: first means for obtaining an absolute value of an amplitude of first and second output signals output from the first block of the photoelectric conversion element; second means for comparing the absolute values with predetermined reference values to obtain differences thereof; first correction means for correcting the first and second output signals on the basis of the differences obtained by the second means; second correction means for correcting third and fourth output signals output from the second block on the basis of the differences obtained by the second means; transfer means for receiving the first and second output signals corrected by the first correction means and the third and fourth output signals corrected by the second correction means, and correcting a pixel arrangement of the output signals, thereby obtaining an original output signal, and then outputting the original output signal; processing means for processing the original output signal which is output from the transfer means and has the original pixel arrangement; and image forming means for forming the image on the basis of the original output signal processed by the processing means.

Claim 15

An image forming apparatus which irradiates a document and forms an image of the document on the basis of a corrected signal output from a photoelectric conversion element having first and second blocks and photoelectrically converting received reflected light from the document, comprising: first means for obtaining an absolute value of an amplitude of first and second output signals output from the first block of the photoelectric conversion element; second means for comparing the absolute values with predetermined reference values to obtain differences thereof; first correction means for correcting the first and second output signals on the basis of the differences obtained by the second means; second correction means for correcting third and fourth output signals output from the second block on the basis of the differences obtained by the second means; transfer means for receiving the first and second output signals corrected by the first correction means and the third and fourth output signals corrected by the second correction means, and correcting a pixel arrangement of the output signals, thereby obtaining an original output signal, and then outputting the original output signal; processing means for processing the original output signal which is output from the transfer means and has the original pixel arrangement; and image forming means for forming the image on the basis of the original output signal processed by the processing means.

Claim 16

An image forming apparatus which irradiates a document and forms an image on the basis of corrected first, second, third, and fourth output signals from a quadruplex photoelectric conversion element dividing image data into four groups and photoelectrically converting received light reflected from the document, comprising: first correction means for dividing the first output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal obtained by the comparison; second correction means for dividing the second output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction means; third correction means for dividing the third output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as the reference value from the first correction means; fourth correction means for dividing the fourth output signal output from the quadruplex photoelectric conversion element into an image signal and, a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as the reference value from the first correction means; transfer means for transferring the image signal corrected by the first correction means, the image signal corrected by the second correction means, the image signal corrected by the third correction means, and the image signal corrected by the fourth correction means by which a pixel arrangements in the output signals are corrected to an original one; processing means for processing the output signals transferred from the transfer means and have the original pixel arrangement; and image forming means for forming the image on the basis of the output signal processed by the processing means.

Claim 17

An image forming apparatus which irradiates a document and forms an image on the basis of corrected first, second, third, and fourth output signals from a quadruplex photoelectric conversion element dividing image data into four groups and photoelectrically converting received light reflected from the document, comprising: first correction means for dividing the first output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal obtained by the comparison; second correction means for dividing the second output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction means; third correction means for dividing the third output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as the reference value from the first correction means; fourth correction means for dividing the fourth output signal output from the quadruplex photoelectric conversion element into an image signal and, a control signal, comparing an absolute value of the control signal with the error signal obtained by the first correction means as a predetermined reference value, and correcting the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as the reference value from the first correction means; transfer means for transferring the image signal corrected by the first correction means, the image signal corrected by the second correction means, the image signal corrected by the third correction means, and the image signal corrected by the fourth correction means by which a pixel arrangements in the output signals are corrected to an original one; processing means for processing the output signals transferred from the transfer means and have the original pixel arrangement; and image forming means for forming the image on the basis of the output signal processed by the processing means.

Claim 18

An image density correction device, comprising: a photoelectric conversion element having first and second blocks, to photoelectrically convert received light; a first circuit which obtains an absolute value of an amplitude of each of first and second output signals output from the first block of the photoelectric conversion element; a second circuit which compares the absolute values with predetermined reference values to obtain differences thereof; a first correction circuit which corrects the first and second output signals on the basis of the differences obtained by the second circuit; and a second correction circuit which corrects third and fourth output signals from the second block on the basis of the differences obtained by the second circuit.

Claim 19

An image density correction device, comprising: a photoelectric conversion element having first and second blocks, to photoelectrically convert received light; a first circuit which obtains an absolute value of an amplitude of each of first and second output signals output from the first block of the photoelectric conversion element; a second circuit which compares the absolute values with predetermined reference values to obtain differences thereof; a first correction circuit which corrects the first and second output signals on the basis of the differences obtained by the second circuit; and a second correction circuit which corrects third and fourth output signals from the second block on the basis of the differences obtained by the second circuit.

Claim 20

An image reading device which irradiates a document and reads an image of the document with use of a photoelectric conversion element having first and second blocks and photoelectrically converting received light reflected from the document by correcting an output signal from the photoelectric conversion element, comprising: a first circuit which obtains an absolute value of an amplitude of each of first and second output signals output from the first block of the photoelectric conversion element; a second circuit which compares the absolute values with predetermined reference values to obtain differences thereof; a first correction circuit which corrects the first and second output signals on the basis of the differences obtained by the second circuit; a second correction circuit which corrects third and fourth output signals output from the second block on the basis of the differences obtained by the second circuit; a transfer circuit which receives the first and second output signals corrected by the first correction circuit and the third and fourth output signals corrected by the second correction circuit, and corrects a pixel arrangement of the output signals, thereby obtaining an original output signal, and then outputs the original output signal; and a processor which processes the original output signal which is output from the transfer circuit and has the original pixel arrangement.

Claim 21

An image reading device which irradiates a document and reads an image of the document with use of a photoelectric conversion element having first and second blocks and photoelectrically converting received light reflected from the document by correcting an output signal from the photoelectric conversion element, comprising: a first circuit which obtains an absolute value of an amplitude of each of first and second output signals output from the first block of the photoelectric conversion element; a second circuit which compares the absolute values with predetermined reference values to obtain differences thereof; a first correction circuit which corrects the first and second output signals on the basis of the differences obtained by the second circuit; a second correction circuit which corrects third and fourth output signals output from the second block on the basis of the differences obtained by the second circuit; a transfer circuit which receives the first and second output signals corrected by the first correction circuit and the third and fourth output signals corrected by the second correction circuit, and corrects a pixel arrangement of the output signals, thereby obtaining an original output signal, and then outputs the original output signal; and a processor which processes the original output signal which is output from the transfer circuit and has the original pixel arrangement.

Claim 22

An image reading device which irradiates a document and reads an image of the document with use of a quadruplex photoelectric conversion element for dividing image data into four groups and photoelectrically converting received light reflected from the document by correcting first, second, third, and fourth output signals from the quadruplex photoelectric conversion element, comprising: a first correction circuit which divides the first output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with a predetermined reference value, and corrects the dividing image signal to have a predetermined voltage with use of an error signal obtained by the comparison; a second correction circuit which divides the second output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a third correction circuit which divides the third output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a fourth correction circuit which divides the fourth output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a transfer circuit which transfers the image signal corrected by the first correction circuit, the image signal corrected by the second correction circuit, the image signal corrected by the third correction circuit, and the image signal corrected by the fourth correction circuit by which pixel arrangements of the image signals are corrected to an original one; and a processor which processes the output signals which are transferred from the transfer circuit and have the original pixel arrangement.

Claim 23

An image reading device which irradiates a document and reads an image of the document with use of a quadruplex photoelectric conversion element for dividing image data into four groups and photoelectrically converting received light reflected from the document by correcting first, second, third, and fourth output signals from the quadruplex photoelectric conversion element, comprising: a first correction circuit which divides the first output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with a predetermined reference value, and corrects the dividing image signal to have a predetermined voltage with use of an error signal obtained by the comparison; a second correction circuit which divides the second output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a third correction circuit which divides the third output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a fourth correction circuit which divides the fourth output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a transfer circuit which transfers the image signal corrected by the first correction circuit, the image signal corrected by the second correction circuit, the image signal corrected by the third correction circuit, and the image signal corrected by the fourth correction circuit by which pixel arrangements of the image signals are corrected to an original one; and a processor which processes the output signals which are transferred from the transfer circuit and have the original pixel arrangement.

Claim 24

An image forming apparatus which irradiates a document and forms an image of the document on the basis of a corrected signal output from a photoelectric conversion element having first and second blocks and photoelectrically converting received reflected light from the document, comprising: a first circuit which obtains an absolute value of an amplitude of first and second output signals output from the first block of the photoelectric conversion element; a second circuit which compares the absolute values with predetermined reference values to obtain differences thereof; a first correction circuit which corrects the first and second output signals on the basis of the differences obtained by the second circuit; a second correction circuit which corrects third and fourth output signals output from the second block on the basis of the differences obtained by the second circuit; a transfer circuit which receives the first and second output signals corrected by the first correction circuit and the third and fourth output signals corrected by the second correction circuit, and corrects a pixel arrangement of the output signals, thereby obtaining an original output signal, and then outputs the original output signal; a processor which processes the original output signal which is output from the transfer circuit and has the original pixel arrangement; and an image forming circuit which forms the image on the basis of the original output signal processed by the processor.

Claim 25

An image forming apparatus which irradiates a document and forms an image of the document on the basis of a corrected signal output from a photoelectric conversion element having first and second blocks and photoelectrically converting received reflected light from the document, comprising: a first circuit which obtains an absolute value of an amplitude of first and second output signals output from the first block of the photoelectric conversion element; a second circuit which compares the absolute values with predetermined reference values to obtain differences thereof; a first correction circuit which corrects the first and second output signals on the basis of the differences obtained by the second circuit; a second correction circuit which corrects third and fourth output signals output from the second block on the basis of the differences obtained by the second circuit; a transfer circuit which receives the first and second output signals corrected by the first correction circuit and the third and fourth output signals corrected by the second correction circuit, and corrects a pixel arrangement of the output signals, thereby obtaining an original output signal, and then outputs the original output signal; a processor which processes the original output signal which is output from the transfer circuit and has the original pixel arrangement; and an image forming circuit which forms the image on the basis of the original output signal processed by the processor.

Claim 26

An image reading device which irradiates a document and reads an image of the document with use of a quadruplex photoelectric conversion element for dividing image data into four groups and photoelectrically converting received light reflected from the document by correcting first, second, third, and fourth output signals from the quadruplex photoelectric conversion element, comprising: a first correction circuit which divides the first output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with a predetermined reference value, and corrects the dividing image signal to have a predetermined voltage with use of an error signal obtained by the comparison; a second correction circuit which divides the second output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a third correction circuit which divides the third output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a fourth correction circuit which divides the fourth output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a transfer circuit which transfers the image signal corrected by the first correction circuit, the image signal corrected by the second correction circuit, the image signal corrected by the third correction circuit, and the image signal corrected by the fourth correction circuit by which pixel arrangements of the image signals are corrected to an original one; a processor which processes the output signals which are transferred from the transfer circuit and have the original pixel arrangement; and an image forming circuit which forms the image on the basis of the output signal processed by the processor.

Claim 27

An image reading device which irradiates a document and reads an image of the document with use of a quadruplex photoelectric conversion element for dividing image data into four groups and photoelectrically converting received light reflected from the document by correcting first, second, third, and fourth output signals from the quadruplex photoelectric conversion element, comprising: a first correction circuit which divides the first output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with a predetermined reference value, and corrects the dividing image signal to have a predetermined voltage with use of an error signal obtained by the comparison; a second correction circuit which divides the second output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a third correction circuit which divides the third output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a fourth correction circuit which divides the fourth output signal output from the quadruplex photoelectric conversion element into an image signal and a control signal, compares an absolute value of the control signal with the error signal obtained by the first correction circuit as a predetermined reference value, and corrects the image signal to have a predetermined voltage with use of an error signal voltage obtained by the comparison of the absolute value and the error signal output as a reference value from the first correction circuit; a transfer circuit which transfers the image signal corrected by the first correction circuit, the image signal corrected by the second correction circuit, the image signal corrected by the third correction circuit, and the image signal corrected by the fourth correction circuit by which pixel arrangements of the image signals are corrected to an original one; a processor which processes the output signals which are transferred from the transfer circuit and have the original pixel arrangement; and an image forming circuit which forms the image on the basis of the output signal processed by the processor.