Clock-generating circuit and image-forming apparatus having a function of canceling unevenness of scanning-light amount

A circuit for generating dot clock pulses for driving a light-emitting element employed in an optical-writing section of an image-forming apparatus, comprising:

• an index sensor to detect a light-beam, which is emitted from said light-emitting element and is deflected for scanning by a light-scanning device employed in said optical-writing section, and to output an index signal when said index sensor detects said light-beam at an end portion of a main-scanning region scanned by said light-beam;
• a delay-chain section to generate a plurality of delayed-clock pulses by delaying clock-pulses, outputted from a reference oscillator, in slightly different delay times;
• a synchronized clock pulse detecting section to select synchronized delayed-clock pulses, which are synchronized with said index signal, out of said plurality of delayed clock pulses generated in said delay-chain section, and to output a number of delay-stages, which is derived from said synchronized delayed-clock pulses, as synchronizing information;
• a table memory to store scanning-light unevenness information, which represents unevenness of scanning-light amounts caused by an optical element employed in said optical-writing section;
• a delayed-clock switching section to generate a select signal, for selecting a specific delayed-clock pulse, having a phase suitable for compensating for said unevenness of scanning-light amount caused by said optical element employed in said optical-writing section, out of said plurality of delayed-clock pulses, based on said synchronized delayed-clock pulses and said synchronizing information outputted from said synchronized clock pulse detecting section and said scanning-light unevenness information stored in said table memory;
• and
• a selector to select said specific delayed-clock pulse out of said plurality of delayed-clock pulses in response to said select signal generated by said delayed-clock switching section.

An image-forming apparatus, comprising:

• an image-forming section that includes an optical-writing section to form an image;
• and
• a circuit for generating dot clock pulses for driving a light-emitting element employed in said optical-writing section included in said image-forming section;
• wherein said circuit includes,
• a digital-delay dot clock adjusting section to adjust timings of rising-edges or falling-edges of said dot clock pulses generated by changing a selection for a plurality of delayed-clock pulses, which are generated by delaying clock-pulses, outputted from a reference oscillator, in slightly different delay times, and
• a controlling section to control a selecting operation for said plurality of delayed clock pulses, performed in said digital-delay dot clock adjusting section, so as to compensate for unevenness of scanning-light amount caused by an optical element employed in said optical-writing section;
• and
• wherein said image-forming section performs an image-forming operation based on clock signals outputted from said digital-delay dot clock adjusting section.

An image-forming apparatus, comprising:

• an image-forming section that includes an optical-writing section to form an image;
• and
• a circuit for generating dot clock pulses for driving a light-emitting element employed in said optical-writing section included in said image-forming section;
• wherein said circuit includes:
• an index sensor to detect a light-beam, which is emitted from said light-emitting element and is deflected for scanning by a light-scanning device employed in said optical-writing section, and to output an index signal when said index sensor detects said light-beam at an end portion of a main-scanning region scanned by said light-beam;
• a delay-chain section to generate a plurality of delayed-clock pulses by delaying clock-pulses, outputted from a reference oscillator, in slightly different delay times;
• a synchronized clock pulse detecting section to select synchronized delayed-clock pulses, which are synchronized with said index signal, out of said plurality of delayed clock pulses generated in said delay-chain section, and to output a number of delay-stages, which is derived from said synchronized delayed-clock pulses, as synchronizing information;
• a table memory to store scanning-light unevenness information, which represents unevenness of scanning-light amounts caused by an optical element employed in said optical-writing section;
• a delayed-clock switching section to generate a select signal, for selecting a specific delayed-clock pulse, having a phase suitable for compensating for said unevenness of scanning-light amount caused by said optical element employed in said optical-writing section, out of said plurality of delayed-clock pulses, based on said synchronized delayed-clock pulses and said synchronizing information outputted from said synchronized clock pulse detecting section and said scanning-light unevenness information stored in said table memory;
• and
• a selector to select said specific delayed-clock pulse out of said plurality of delayed-clock pulses in response to said select signal generated by said delayed-clock switching section;
• and
• wherein said image-forming section performs an image-forming operation based on clock signals outputted from said selector.