Light beam scanning apparatus

A light beam scanning apparatus comprising:

• a light emitting device which outputs a light beam;
• a light beam scanning member which allows a light beam output from the light emitting device to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• a pair of sensors which are arranged on said scanned face or a position equivalent thereto, which detect a light beam scanned by said light beam scanning member, and which output an electric signal;
• a processing circuit which has a plurality of operational amplifiers, which corrects an output from each of said pair of sensors to obtain corrected electric signals, and which integrates a difference between the corrected electric signals;
• a control section which determines the necessity of correction based on a value integrated by the processing circuit, which determines a scanning position of said light beam according to a value integrated by said processing circuit when the necessity of correction is not determined, and which sets a correction amount based on a value integrated by said processing circuit and an offset amount present in each operational amplifier in said processing circuit when the necessity of correction is determined;
• a correction signal generation circuit which outputs a correction signal to said processing circuit so as to correct an electric signal output from each of said pair of sensors based on a correction amount set in the control section;
• and
• a memory which stores a correction amount,
• wherein said control section sets a correction amount based on a value integrated by said processing circuit, an offset amount present in said processing circuit, and a previous correction amount stored in said memory.

A light beam scanning apparatus comprising:

• a light emitting device which outputs a light beam;
• a light beam scanning member which allows a light beam output from this light emitting device to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• a pair of sensors which are arranged on said scanned face or a position equivalent thereto, detect a light beam scanned by said light beam scanning member, and output an electric signal;
• an integrator circuit which integrates a difference between electric signals output from each of said pair of sensors;
• a first comparator circuit which compares a value integrated in this integrator circuit with a first threshold;
• a second comparator circuit which compares a value integrated in said integrator circuit with a second threshold smaller than said first threshold;
• and
• a decision section which specifies first and second thresholds to said first and second comparator circuits, uses said first and second comparator circuits to repeat comparison among said integrator circuit's output value and said first and second thresholds for a plurality of times, and determines magnitude relation among said integrator circuit's average output value and said first and second thresholds based on the number of times for determining said integrator circuit's output value to be greater than said first threshold, the number of times for determining said integrator circuit's output value to be between said first and second thresholds, and the number of times for determining said integrator circuit's output value to be smaller than said second threshold.

An image forming apparatus having an image support to form a latent image on a scanned face where a light beam is scanned based on image information, and

• image formation means for forming an image formed on the image support onto an image formation medium, said image formation apparatus comprising:
• a light emitting device which outputs a light beam;
• a light beam scanning member which allows a light beam output from the light emitting device to scan said light beam toward said scanned face so that said light beam scans said scanned face on said image support in a main scanning direction;
• a pair of sensors which are arranged on said scanned face or a position equivalent thereto, which detect a light beam scanned by said light beam scanning member, and which output an electric signal;
• a processing circuit which has a plurality of operational amplifiers, which corrects an output from each of said pair of sensors to obtain corrected electric signals, and which integrates a difference between the corrected electric signals;
• a control section which determines the necessity of correction based on a value integrated by the processing circuit, which determines a scanning position of said light beam according to a value integrated by said processing circuit when the necessity of correction is not determined, and which sets a correction amount based on a value integrated by said processing circuit and an offset amount present in each operational amplifier in said processing circuit when the necessity of correction is determined;
• and
• a correction signal generation circuit which outputs a correction signal to said processing circuit so as to correct an electric signal output from each of said pair of sensors based on a correction amount set in the control section,
• wherein said control section sets a correction amount for each specified correction width based on a value integrated by said processing circuit and an offset amount present in each operational amplifier in said processing circuit and further sets a correction amount by using a finer correction width than said specified correction width when said specified correction width cannot detect a passage position of said light beam.

An image forming apparatus having an image support to form a latent image on a scanned face where a light beam is scanned based on image information, and

• image formation means for forming an image formed on the image support onto image formation medium, said image formation apparatus comprising:
• a light emitting device which outputs a light beam;
• a light beam scanning member which allows a light beam output from the light emitting device to scan said light beam toward said scanned face so that said light beam scans said scanned face on said image support in a main scanning direction;
• a pair of sensors which are arranged on said scanned face or a position equivalent thereto, which detect a light beam scanned by said light beam scanning member, and which output an electric signal;
• a processing circuit which has a plurality of operational amplifiers, which corrects an output from each of said pair of sensors to obtain corrected electric signals, and which integrates a difference between the corrected electric signals;
• a control section which determines the necessity of correction based on a value integrated by the processing circuit, which determines a scanning position of said light beam according to a value integrated by said processing circuit when the necessity of correction is not determined, and which sets a correction amount based on a value integrated by said processing circuit and an offset amount present in each operational amplifier in said processing circuit when the necessity of correction is determined;
• a correction signal generation circuit which outputs a correction signal to said processing circuit so as to correct an electric signal output from each of said pair of sensors based on a correction amount set in the control section;
• and
• a memory which stores a correction amount,
• wherein said control section sets a correction amount based on a value integrated by said processing circuit, an offset amount present in said processing circuit, and a previous correction amount stored in said memory.

An image formation apparatus having an image support to form a latent image on a scanned face where a light beam is scanned based on image information and

• image formation means for forming an image formed on this image support
• onto an image formation medium, said image formation apparatus comprising:
• a light emitting device which outputs a light beam;
• a light beam scanning member which allows a light beam output from this light emitting device to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• a pair of sensors which are arranged on said scanned face or a position equivalent thereto, detect a light beam scanned by said light beam scanning member, and output an electric signal;
• an integrator circuit which integrates a difference between electric signals output from each of said pair of sensors;
• a first comparator circuit which compares a value integrated in this integrator circuit with a first threshold;
• a second comparator circuit which compares a value integrated in said integrator circuit with a second threshold smaller than said first threshold;
• and
• a decision section which specifies first and second thresholds to said first and second comparator circuits, uses said first and second comparator circuits to repeat comparison among said integrator circuit's output value and said first and second thresholds for a plurality of times, and determines magnitude relation among said integrator circuit's average output value and said first and second thresholds based on the number of times for determining said integrator circuit's output value to be greater than said first threshold, the number of times for determining said integrator circuit's output value to be between said first and second thresholds, and the number of times for determining said integrator circuit's output value to be smaller than said second threshold.

A light beam scanning apparatus comprising:

• light emitting means for outputting a light beam;
• light beam scanning means for allowing a light beam output from the light emitting means to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• a pair of detection means, arranged on said scanned face or a position equivalent thereto, for detecting a light beam scanned by said light beam scanning means and outputting an electric signal;
• processing means having a plurality of operational amplifiers for correcting an output from each of said pair of detection means to obtain. corrected electric signals, and for integrating a difference between the corrected electric signals;
• control means for determining the necessity of correction based on a value integrated by said processing means, determining a scanning position of said light beam according to a value integrated by said processing means when the necessity of correction is not determined, and setting a correction amount based on a value integrated by said processing means and an offset amount present in said operational amplifier in said processing means when the necessity of correction is determined;
• and
• correction signal generation means for outputting a correction signal to said processing means so as to correct an electric signal output from each of said pair of detection means based on a correction amount set in said control means,
• wherein said control means sets a correction amount for each specified correction width based on a value integrated by said processing means and an offset amount present in each operational amplifier in said processing means and further sets a correction amount by using a finer correction width than said specified correction width when said specified correction width cannot detect a passage position of said light beam.

A light beam scanning apparatus comprising:

• light emitting means for outputting a light beam;
• light beam scanning means for allowing a light beam output from the light emitting means to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• a pair of detection means, arranged on said scanned face or a position equivalent thereto, for detecting a light beam scanned by said light beam scanning means and outputting an electric signal;
• processing means having a plurality of operational amplifiers for correcting an output from each of said pair of detection means to obtain corrected electric signals, and for integrating a difference between the corrected electric signals;
• control means for determining the necessity of correction based on a value integrated by the processing means, determining a scanning position of said light beam according to a value integrated by said processing means when the necessity of correction is not determined, and setting a correction amount based on a value integrated by said processing means and an offset amount present in each operational amplifier in said processing means when the necessity of correction is determined;
• correction signal generation means for outputting a correction signal to said processing means so as to correct an electric signal output from each of said pair of detection means based on a correction amount set in said control means;
• and
• storage means for storing a correction amount,
• wherein said control means sets a correction amount based on a value integrated by said processing means, an offset amount present in each operational amplifier in said processing means, and a previous correction amount stored in said storage means.

A light beam scanning apparatus comprising:

• light emitting means for outputting a light beam;
• light beam scanning means for allowing a light beam output from this light emitting means to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• a pair of detection means, arranged on said scanned face or a position equivalent thereto, for detecting a light beam scanned by said light beam scanning means and outputting an electric signal;
• integration means for integrating a difference between electric signals output from each of said pair of detection means;
• first comparison means for comparing a value integrated in this integration means with a first threshold;
• second comparison means for comparing a value integrated in said integration means with a second threshold smaller than said first threshold;
• and
• decision means for specifying first and second thresholds to said first and second comparator means, using said first and second comparison means to repeat comparison among said integration means' output value and said first and second thresholds for a plurality of times, and determining magnitude relation among said integration means' average output value and said first and second thresholds based on the number of times for determining said integration means' output value to be greater than said first threshold, the number of times for determining said integration means' output value to be between said first and second thresholds, and the number of times for determining said integration means' output value to be smaller than said second threshold.

A method of detecting a light beam passage position comprising:

• generating a light beam;
• allowing a generated light beam to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• converting a light beam scanning said scanned face to an electric signal by using a pair of sensors arranged on said scanned face or a position equivalent thereto;
• correcting an electric signal converted from each of said plurality of sensors based on a correction signal and integrating a difference between the corrected electric signals by using a processing circuit having a plurality of operational amplifiers;
• determining the necessity of correction based on the integrated value, determining a scanning position of said light beam according to a value integrated by said processing circuit when the necessity of correction is not determined, and setting a correction amount based,on a value integrated by said processing circuit and an offset amount present in each operational amplifier in said processing circuit when the necessity of correction is determined;
• and
• outputting a correction signal to said processing circuit so as to correct an electric signal output from each of said pair of sensors based on the set correction amount,
• when setting said correction amount, setting a correction amount for each specified correction width based on a value integrated by said processing circuit and an offset amount present in each operational amplifier in said processing circuit and further setting a correction amount by using a finer correction width than said specified correction width when said specified correction width cannot detect a passage position of said light beam.

A method of detecting a light beam passage position comprising:

• generating a light beam;
• allowing a generated light beam to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• converting a light beam scanning said scanned face to an electric signal by using a pair of sensors arranged on said scanned face or a position equivalent thereto;
• correcting an electric signal converted from each of said plurality of sensors based on a correction signal and integrating a difference between the corrected electric signals by using a processing circuit having a plurality of operational amplifiers;
• determining the necessity of correction based on the integrated value, determining a scanning position of said light beam according to a value integrated by said processing circuit when the necessity of correction is not determined, and setting a correction amount based on a value integrated by said processing circuit and an offset amount present in each operational amplifier in said processing circuit when the necessity of correction is determined;
• outputting a correction signal to said processing circuit so as to correct an electric signal output from each of said pair of sensors based on the set correction amount;
• and
• storing a previous correction amount in a memory;
• and
• when setting said correction amount, setting a correction amount based on a value integrated by said processing circuit, an offset amount present in said processing circuit, and a previous correction amount stored in said memory.

A method of detecting a light beam passage position comprising:

• generating a light beam;
• allowing a generated light beam to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• converting a light beam scanning said scanned face to an electric signal by using a pair of sensors arranged on said scanned face or a position equivalent thereto;
• integrating a difference between electric signals converted by each of said pair of sensors by using an integrator circuit;
• comparing the integrated value with a first threshold by using a first comparator circuit;
• comparing said integrated value with a second threshold smaller than said first threshold by using a second comparator circuit;
• and
• specifying first and second thresholds, repeating comparison among said values integrated by said first and second comparator circuits and said first and second thresholds for a plurality of times, and determining magnitude relation among an average value of said integrated values and said first and second thresholds based on the number of times for determining said integrated value to be greater than said first threshold, the number of times for determining said integrated value to be between said first and second thresholds, and the number of times for determining said integrated value to be smaller than said second threshold.

A light beam scanning apparatus comprising:

• a light emitting device which outputs a light beam;
• a light beam scanning member which allows the light beam output from the light emitting device to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• a light beam passage position detection section configured so that its output continuously varies in accordance with a change of a position where the light beam passes through when the passage position of the light beam passes through in a direction orthogonal to the main scanning direction is within a predetermined detection range;
• a determination section which determines whether or not the passage position of the light beam scanned by the light beam scanning member on the scanned face in a direction orthogonal to the scanning direction is within the predetermined detection range;
• a detection range correction section which shifts the detection range of the light beam passage position detection section;
• and
• a control section which causes the detection range correction section to shift the detection range of the light beam passage position detection section such that the light beam passage position detection section detects the passage position of the light beam when the determination section has determined that the light beam does not scan within the detection range.

A light beam scanning apparatus comprising:

• a circuit whose output continuously varies in accordance with a change of a passage position of a light beam;
• a setting section which sets a first threshold and a second threshold different from the first threshold;
• a first comparator circuit which compares an output value of the circuit with the first threshold;
• a second comparator circuit which compares the output value of the circuit with the second threshold;
• a determination section which determines the output value of the circuit based on the comparison results by the first and second comparator circuits;
• a change section which changes the first and second thresholds preset by the setting section;
• and
• a control section which, when the output value of the circuit cannot be determined based on the comparison results of the first and second comparator circuits, causes the change section to change the preset first and second thresholds in accordance with the first and second thresholds at the time of the output value of the circuit being undeterminable, causes the first and second comparator circuits to compare again, and causes the determination section to determine the output value of the circuit.

A light beam scanning apparatus comprising:

• a circuit whose output continuously varies in accordance with a shift of a passage position of a light beam;
• a setting section which sets a first threshold and a second threshold different from the first threshold;
• a first comparator circuit which compares an output value of the circuit with the first threshold;
• a second comparator circuit which compares the output value of the circuit with the second threshold;
• a control section which causes the first and second comparator circuits to repeatedly execute comparison processing between the output value of the circuit and the first and second thresholds for a plurality of times;
• and
• a deciding section which, when the comparison processing by the first and second comparison circuits are executed a plurality of times, decides an average output value of the circuit in accordance with the comparison results between the first threshold and the output value of the circuit and those between the second threshold and the output value of the circuit.

An image formation apparatus having an image support to form a latent image on a scanned face where a light beam is scanned based on image information and an image formation means for forming an image formed on this image support onto an image formation medium, said image formation apparatus comprising:

• a light emitting device which outputs a light beam;
• a light beam scanning member which allows the light beam output from the light emitting device to scan toward a scanned face, so that said light beam scans said scanned face in a main scanning direction;
• a light beam passage position detection section configured so that its output continuously varies in accordance with a change of a passage position of the light beam when the passage position of the light beam in a direction orthogonal to the main scanning direction is within a predetermined detection range;
• a determination section which determines whether or not the passage position of the light beam scanned by the light beam scanning member on the scanned face in a direction orthogonal to the scanning direction is within the predetermined detection range;
• a detection range correction section which shifts the detection range of the light beam passage position detection section;
• and
• a control section which causes the detection range correction section to shift the detection range of the light beam passage position detection section such that the light beam passage position detection section detects the passage position of the light beam when the determination section has determined that the light beam does not scan within the detection range.

An image formation apparatus having an image support to form a latent image on a scanned face where a light beam is scanned based on image information and an image formation means for forming an image formed on this image support onto an image formation medium, said image formation apparatus comprising:

• a circuit whose output continuously varies in accordance with a change of a passage position of a light beam;
• a setting section which sets a first threshold and a second threshold different from the first threshold;
• a first comparator circuit which compares an output value of the circuit with the first threshold;
• a second comparator circuit which compares the output value of the circuit with the second threshold;
• a determination section which determines the output value of the circuit based on the comparison results by the first and second comparator circuits;
• a change section which changes the first and second thresholds preset by the setting section;
• and
• a control section which, when the output value of the circuit cannot be determined based on the comparison results by the first and second comparator circuits, causes the change section to change the preset first and second thresholds in accordance with the first and second thresholds at the time of the output value of the circuit being undeterminable, causes the first and second comparator circuits to compare again, and causes the determination section to determine the output value of the circuit.

An image formation apparatus having an image support to form a latent image on a scanned face where a light beam is scanned based on image information and an image formation means for forming an image formed on this image support onto an image formation medium, said image formation apparatus comprising:

• a circuit whose output continuously varies in accordance with a shift of a passage position of a light beam;
• a setting section which sets a first threshold and a second threshold different from the first threshold;
• a first comparator circuit which compares an output value of the circuit with the first threshold;
• a second comparator circuit which compares the output value of the circuit with the second threshold;
• a control section which causes the first and second comparator circuits to repeatedly execute comparison processing between the output value of the circuit and the first and second thresholds for a plurality of times;
• and
• a deciding section which, when the comparison processing by the first and second comparison circuits are executed a plurality of times, decides an average output value of the circuit in accordance with the comparison results between the first threshold and the output value of the circuit and those between the second threshold and the output value of the circuit.

A light beam scanning apparatus comprising:

• light emitting means for outputting the light beam;
• light beam scanning means for allowing a light beam output from the light emitting means to scan toward a scanned face, so that said light beam scans said scanned face in a main scanning direction;
• light beam passage position detection means configured so that its output continuously varies in accordance with a change of a passage position of the light beam when the passage position of the light beam in a direction orthogonal to the main scanning direction is within a predetermined detection range;
• determination means for determining whether or not the passage position of the light beam scanned by the light beam scanning means on the scanned face in a direction orthogonal to the scanning direction is within the range detected by the light beam passage position detection means;
• detection range correction means for shifting the detection range of the light beam passage position detection means;
• and
• control means for causing the detection range correction means to shift the detection range of the light beam passage position detection means such that the light beam passage position detection means detects the passage position of the light beam when the determination means has determined that the light beam does not scan within the detection range.

A light beam scanning apparatus comprising:

• output means whose output continuously varies in accordance with a change of a passage position of a light beam;
• setting means for setting a first threshold and a second threshold;
• first comparator means for comparing an output value of the output means with the first threshold;
• second comparator means for comparing the output value of the output means with the second threshold;
• determination means for determining the output value of the output means based on the comparison results by the first and second comparator means;
• change means for changing the first and second thresholds set by the setting means;
• and
• control means for, when the output value of the output means cannot be determined based on the comparison results by the first and second comparator means, causing the change means to change the set first and second thresholds in accordance with the first and second thresholds at the time of the output value of the output means being undeterminable, causing the first and second comparator means to compare again, and causing the determination means to determine the output value of the output means.

A light beam scanning apparatus comprising:

• output means whose output continuously varies in accordance with a shift of a passage position of a light beam;
• setting means for setting a first threshold and a second threshold different from the first threshold;
• first comparator means for comparing an output value of the output means with the first threshold;
• second comparator means for comparing the output value of the output means with the second threshold;
• control means for causing the first and second comparator means to repeatedly execute comparison processing between the output value of the output means and the first and second thresholds for a plurality of times;
• and
• deciding means for, when the comparison processing by the first and second comparison means are executed a plurality of times, deciding an average output value of the output means in accordance with the comparison results between the first threshold and the output value of the output means and those between the second threshold and the output value of the output means.

A light beam scanning method comprising:

• emitting a light beam;
• allowing the emitted light beam to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction;
• allowing a light beam passage position detection section to detect the light beam, the light beam passage position detection section being configured so that its output continuously varies in accordance with a change of a passage position of the light beam when the passage position of the light beam in a direction orthogonal to the main scanning direction is within a predetermined detection range;
• determining whether or not the passage position of the light beam scanned on the scanned face in a direction orthogonal to the scanning direction is within the detection range of the light beam passage position detection section;
• shifting the detection range of the light beam passage position detection section when it is determined that the light beam does not scan within the detection range of the light beam passage position detection section.

A method of detecting a light beam passage position comprising:

• setting a first threshold and a second threshold different from the first threshold;
• allowing a first comparator circuit to compare an output value of a circuit whose output value continuously varies in accordance with a change of a passage position of the light beam with the first threshold;
• allowing a second comparator circuit to compare the output value of the circuit with the second threshold;
• determining the output value of the circuit based on the comparison results by the first and second comparator circuits;
• changing set first and second threshold values, when the output value of the circuit cannot be determined based on the comparison results by the first and second comparator circuits, in accordance with the first and second thresholds at the time of the output value of the circuit being undeterminable;
• and
• determining the output value of the circuit by re-performing comparison processing by the first and second comparator circuits when the first and second thresholds are changed.

A method of detecting a light beam passage position comprising:

• setting a first threshold and a second threshold different from the first threshold;
• allowing a first comparator circuit to compare an output value of a circuit whose output continuously varies in accordance with a shift of a passage position of a light beam with the first threshold;
• allowing a second comparator circuit to compare the output value of the circuit with the second threshold;
• allowing the first and second comparator circuits to repeatedly execute comparison processing between the output value of the circuit and the first and second thresholds for a plurality of times;
• and
• deciding an average output value of the output values of the circuit in accordance with the comparison results between the first threshold and the output value of the circuit and those between the second threshold and the output value of the circuit, when the comparison processing by the first and second comparison circuits are executed a plurality of times.