Light-emitting element array drive device, print head, image forming apparatus and signal supplying method

A print head comprising:

• an exposure unit that exposes an image carrier;
• and
• an optical unit that focuses light emitted by the exposure unit onto the image carrier,
• the exposure unit including:
• a light-emitting device that includes a plurality of light-emitting elements, and a plurality of switch elements that are electrically connected respectively to the plurality of light-emitting elements and that are electrically connected mutually in an array, each of the switch elements, when turned on, setting one of the light-emitting elements connected thereto ready to emit light, and, when turned off, setting the one of the light-emitting elements connected thereto unready to emit light;
• a transfer signal supply unit that supplies transfer signals for propagating a turned-on state among the plurality of switch elements by sequentially switching each of the switch elements from a turned-off state to the turned-on state, and to the turned-off state, the transfer signals having periods during each of which one of the switch elements is turned on, the periods being displaced so that each two of the periods for two of the switch elements adjacently-connected have an overlapping period, the two of the switch elements being both turned on during the overlapping period;
• and
• a light-emission signal supply unit that supplies a light-emission signal having light-emitting periods during each of which one of the light-emitting elements is turned on, each of the light-emitting periods having an end point set based on a start point of the overlapping period during which the transfer signals start to turn on both of the two of the switch elements adjacently-connected are supplied, and each of the light-emitting periods having a start point set to a time point before the end point.

An image forming apparatus comprising:

• an exposure unit that exposes an image carrier so as to form an electrostatic latent image thereon;
• an optical unit that focuses light emitted by the exposure unit onto the image carrier;
• a developing unit that develops the electrostatic latent image formed on the image carrier, and
• a transfer unit that transfers an image developed on the image carrier onto a transferred body,
• the exposure unit including:
• a charging unit that charges the image carrier;
• a plurality of light-emitting devices each of which includes a plurality of light-emitting elements, and a plurality of switch elements that are electrically connected respectively to the plurality of light-emitting elements and that are electrically connected mutually in an array, each of the switch elements, when turned on, setting one of the light-emitting elements connected thereto ready to emit light, and, when turned off, setting the one of the light-emitting elements connected thereto unready to emit light;
• a transfer signal supply unit that supplies transfer signals for propagating a turned-on state among the plurality of switch elements by sequentially switching each of the switch elements from a turned-off state to the turned-on state, and to the turned-off state, the transfer signals having periods during each of which one of the switch elements is turned on, the periods being displaced so that each two of the periods for two of the switch elements adjacently-connected have an overlapping period, the two of the switch elements being both turned on during the overlapping period;
• and
• a light-emission signal supply unit that supplies a light-emission signal having light-emitting periods during each of which one of the light-emitting elements is turned on, each of the light-emitting periods having an end point set based on a start point of the overlapping period during which the transfer signals start to turn on both of the two of the switch elements adjacently-connected are supplied, and each of the light-emitting periods having a start point set to a time point before the end point.

A signal supplying method for a light-emitting element array drive device including a plurality of light-emitting elements, and a plurality of switch elements that are electrically connected respectively to the plurality of light-emitting elements and that are electrically connected mutually in an array, each of the switch elements, when turned on, setting one of the light-emitting elements connected thereto ready to emit light, and, when turned off, setting the one of the light-emitting elements connected thereto unready to emit light;

• the signal supplying method comprising:
• supplying transfer signals for propagating a turned-on state among the plurality of switch elements by sequentially switching each of the switch elements from a turned-off state to the turned-on state, and to the turned-off state, the transfer signals having periods during each of which one of the switch elements is turned on, the periods being displaced so that each two of the periods for two of the switch elements adjacently-connected have an overlapping period, the two of the switch elements being both turned on during the overlapping period;
• and
• supplying a light-emission signal having light-emitting periods during each of which one of the light-emitting elements is turned on, each of the light-emitting periods having an end point set based on a start point of the overlapping period during which the transfer signals start to turn on both of the two of the switch elements adjacently-connected are supplied, and each of the light-emitting periods having a start point set to a time point before the end point.