Patent Publication Number: US-9417552-B2

Title: Light-emitting element array module and method of controlling light-emitting element array chips

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to, and claims the priority benefit of, Korean Patent Application No. 10-2014-0011734, filed on Jan. 29, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     1. Field 
     One or more embodiments relate to light-emitting element array modules and methods of controlling light-emitting element array chips. 
     2. Description of the Related Art 
     An image forming apparatus using light-emitting element array chips receives print data from a personal computer (PC) and forms an image by using light-emitting elements. When the light-emitting elements emit light, an electrostatic latent image is formed on a photoconductor drum in the image forming apparatus. Thereafter, a print image is output through development, transfer, and fusing processes. 
     The light-emitting element array chips may be connected to a control unit by wire bonding. Therefore, as many wire bondings as the number of signals output from the control unit are required. 
     SUMMARY 
     One or more embodiments include light-emitting element array modules and methods of controlling light-emitting element array chips. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     According to one or more embodiments, a light-emitting element array module includes a control driver configured to receive print data and operate according to the received print data, and light-emitting element array chips configured to receive a signal from the control driver and operate according to the received signal, wherein the control driver applies a start signal to a transfer element array by using a signal applied to a light-emitting element array of the light-emitting element array chips. 
     The control driver may control an operation point of the light-emitting element array chips by separately applying a start signal to the light-emitting element array chips. 
     The control driver may correct a registration error in a main scanning direction of the light-emitting element array chips by controlling a timing to apply a start signal to the light-emitting element array chips according to the registration error. 
     The control driver may correct an image in a main scanning direction by controlling an exposure timing by controlling a timing of a start signal input to the light-emitting element array chips. 
     The transfer element array may include a plurality of transfer elements, and the control driver may apply a start signal having a higher voltage than a high-level voltage of a transfer signal for controlling on/off of the transfer elements. 
     According to one or more embodiments, a light-emitting element array module includes a control driver configured to receive print data and operate according to the received print data, and light-emitting element array chips including a light-emitting element array and a transfer element array, wherein a start signal input terminal of the transfer element array and a data signal input terminal of the light-emitting element array are connected to an output terminal of the control driver. 
     The light-emitting element array module may include a voltage drop element connected between the start signal input terminal of the transfer element array and the data signal input terminal of the light-emitting element array. 
     The light-emitting element array module may include a diode connected in a forward direction between the start signal input terminal of the transfer element array and the data signal input terminal of the light-emitting element array. 
     The light-emitting element array module may include a Zener diode connected between the start signal input terminal of the transfer element array and the data signal input terminal of the light-emitting element array. 
     The light-emitting element array module may include a resistor connected between the start signal input terminal of the transfer element array and the data signal input terminal of the light-emitting element array. 
     The control driver may include a memory storing information about an operation point of the light-emitting element array chips. 
     The light-emitting element array may include a plurality of light-emitting thyristors, and the transfer element array may include a plurality of transfer thyristors. 
     The control driver may include a data transfer unit configured to output a data signal indicating on/off of light-emitting elements, and a start signal generating unit configured to output a start signal for operating transfer elements. 
     The control driver may include a switch configured to connect any one of the data transfer unit and the start signal generating unit to an on-signal output terminal. 
     According to one or more embodiments, a method of controlling light-emitting element array chips includes receiving print data, and controlling the light-emitting element array chips based on the print data, wherein the controlling of the light-emitting element array chips includes applying a start signal to a transfer element array by using a signal applied to a light-emitting element array of the light-emitting element array chips. 
     According to one or more embodiments, an image forming apparatus includes, a control driver configured to operate according to print data received from a personal computer (PC), and a light-emitting element array module configured to form an electrostatic latent image under the control of the control driver, wherein the light-emitting element array module includes light-emitting element array chips including a light-emitting element array and a transfer element array, and a start signal input terminal of the transfer element array and a data signal input terminal of the light-emitting element array are connected to an output terminal of the control driver. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a diagram illustrating an exemplary process of outputting an image by using a light-emitting element array; 
         FIG. 2  is a diagram illustrating a light-emitting element array module according to an embodiment; 
         FIG. 3  is a diagram illustrating an example of a light-emitting element array module according to an embodiment; 
         FIG. 4  is an exemplary block diagram of a light-emitting element array module according to an embodiment; 
         FIG. 5  is an exemplary block diagram of a light-emitting element array module according to an embodiment; 
         FIG. 6  is an exemplary block diagram of a light-emitting element array module according to an embodiment; 
         FIG. 7  is a diagram illustrating an example of a light-emitting element array chip according to an embodiment; 
         FIG. 8  is a diagram illustrating an example of a light-emitting element array chip according to an embodiment; 
         FIG. 9  is a diagram illustrating an example of a light-emitting element array chip according to an embodiment; 
         FIG. 10  is an exemplary timing diagram of signals output from a control driver; 
         FIG. 11  is an exemplary timing diagram of signals output from the control driver; 
         FIG. 12  is a diagram illustrating an exemplary method of transferring a start signal and a data signal; and 
         FIG. 13  is a flowchart of a method of controlling a light-emitting element array chip according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     Various embodiments and modifications, and exemplary embodiments are illustrated in the drawings and are described in detail. However, it will be understood that exemplary embodiments include modifications, equivalents, and substitutions falling within the spirit and scope of the present invention. 
     Although terms such as “first” and “second” may be used herein to describe various elements or components, these elements or components should not be limited by these terms. These terms are used to distinguish one element or component from another element or component. 
     The terms used herein describe exemplary embodiments and are not intended to limit the scope of the present invention. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be understood that terms such as “comprise”, “include”, and “have”, when used herein, do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof. 
     Hereinafter, embodiments are described in detail with reference to the accompanying drawings. In the following description, like reference numerals denote like elements, and redundant descriptions thereof are omitted. 
       FIG. 1  is a diagram illustrating a process of outputting an image by using a light-emitting element array. As illustrated in  FIG. 1 , upon receiving print data from a personal computer (PC)  50 , an image forming apparatus performs operations for outputting an image. 
     The image forming apparatus forms an electrostatic latent image on a photoconductor drum  300  by using light-emitting elements and outputs an image through development, transfer, and fusing processes including electrification  1 , exposure  2 , development  3 , transfer  4  and fixing  5 . 
     The image forming apparatus includes a control driver  110 , a chip array  120 , a lens array  200 , and the photoconductor drum  300 . 
     The control driver  110  controls the chip array  120  according to the print data received from the PC  50 . The chip array  120  includes a plurality of light-emitting element array chips. The control driver  110  may separately control the light-emitting element array chips. An exemplary method of controlling light-emitting element array chips by the control driver  110  is illustrated in  FIG. 2 . 
     The lens array  200  is arranged in an axial direction (i.e., a main scanning direction) of the photoconductor drum  300 . Light having passed through the lens array  200  forms an image on a surface of the photoconductor drum  300 . 
     The photoconductor  300  is exposed to light to form an electrostatic latent image. A developer (not shown) develops the electrostatic latent image formed on the photoconductor drum  300 . 
       FIG. 2  is a diagram illustrating a light-emitting element array module  100  according to an embodiment. As illustrated in  FIG. 2 , the light-emitting element array module  100  may correct a registration error of light-emitting element array chips  125 . A registration error in the main scanning direction may exist between the light-emitting element array chips  125 . When light-emitting element array chips  125  emit light at the same point, the registration error between the light-emitting element array chips  125  may not have been corrected. Thus, the light-emitting element array module  100  may correct the registration error of the light-emitting element array chips  125  by separately controlling the light-emitting element array chips  125 . 
     The control driver  110  receives print data and operates according to the received print data. The control driver  110  receives print data from a central processing unit (CPU) or a main board included in the image forming apparatus, and controls the on/off of light-emitting elements according to the received print data. The print data is data representing an image to be formed. The control driver  110  controls the on/off of the light-emitting elements according to the print data, and controls a start point of the light-emitting element array chips  125  in consideration of the registration error of the light-emitting element array chips  125 . 
     The control driver  110  includes a memory storing information about an operation point of the light-emitting element array chips  125 . In other words, the control driver  110  prestores information about a registration error of the light-emitting element array chips  125 , and prestores information about the operation point of the light-emitting element array chips  125  in the memory according to the registration error. 
     The control driver  110  controls the operation point of the light-emitting element array chips  125  by separately applying a start signal to the light-emitting element array chips  125 . The control driver  110  corrects a registration error in the main scanning direction of the light-emitting element array chips  125  by controlling a timing to apply the start signal to the light-emitting element array chips  125  according to the registration error. In other words, the control driver  110  corrects an image in the main scanning direction by controlling an exposure timing by controlling a timing of the start signal input to the light-emitting element array chips  125 . 
     The control driver  110  does not output the start signal to the light-emitting element array chip  125 , for example, whose print data is all white, among the light-emitting element array chips  125 . When the light-emitting element array chip  125  does not need to emit light, the control driver  110  does not output the start signal to the light-emitting element array chip  125 . Since the control driver  110  may separately control the light-emitting element array chips  125 , the control driver  110  does not output the start signal to the light-emitting element array chip  125 , for example, whose print data is all white, thereby reducing unnecessary power consumption. When print data is all white, there may be no print data, that is, there may be no image to be formed. 
     The light-emitting element array module  100  includes the control driver  110  and the chip array  120 . The chip array  120  includes a plurality of light-emitting element array chips  125 . The control driver  110  and the light-emitting element array chips  125  may be connected by wires. 
     The light-emitting element array chips  125  receive a signal from the control driver  110  and operate according to the received signal. The light-emitting element array chips  125  operate according to the start signal received from the control driver  110 , and emit light according to an on signal. The light-emitting element array chips  125  may be arranged, for example, in a zigzag manner, for example, in lines, e.g., in two lines. 
       FIG. 3  is a diagram illustrating an example of the light-emitting element array module  100  according to an embodiment. 
     The control driver  110  outputs the start signal and the on signal to the light-emitting element array chips  125  through terminals φi 1  to φi 5 . Thus, the control driver  110  may separately control the light-emitting element array chips  125 . The start signal and the on signal may be distinguished from each other by signal levels. 
     Terminals φs 1  to φs 5  of the light-emitting element array chips  125  may be connected in parallel to the terminals φi 1  to φi 5  of the light-emitting element array chips  125 , respectively. For example, the terminals φi 1  and φs 1  of the light-emitting element array chips  125  may be connected in parallel to each other. Thus, a separate wire for connecting the control driver  110  and the terminals φs 1  to φs 5  of the light-emitting element array chips  125  is not necessary. 
     The control driver  110  outputs a transfer signal through terminals φ 1  and φ 2 . The same φ 1  transfer signal and φ 2  transfer signal are received by the light-emitting element array chips  125 . 
       FIG. 4  is an exemplary block diagram of a light-emitting element array module  400  according to an embodiment. As illustrated in  FIG. 4 , a voltage drop element  128  may be connected between a transfer element array  126  and a terminal φs of the light-emitting element array chip  425 . 
     The control driver  110  applies signals to the transfer element array  126  and a light-emitting element array  127  of the light-emitting element array chips  425 . 
     The transfer element array  126  includes a plurality of transfer elements that operate based on a start signal and a transfer signal. 
     The light-emitting element array  127  includes a plurality of light-emitting elements that operate based on an on signal. 
     The light-emitting conditions of the light-emitting elements may be determined according to the states of the transfer elements. The transfer elements and the light-emitting elements may be one-to-one matched. In order for a light-emitting element to emit light, a transfer element corresponding to the light-emitting element has to be in a standby state. When the transfer element is in a standby state, the on/off of the light-emitting element may be determined according to an on signal input to the light-emitting element. When a start signal is input to the transfer elements, the transfer elements sequentially enter a standby state according to a transfer signal. 
     The control driver  110  outputs a start signal to the transfer element array  126  by using a signal applied to the light-emitting element array  127 . The control driver  110  outputs a start signal to the transfer element array  126  through a terminal φi. After outputting the start signal, the control driver  110  outputs an on signal to the light-emitting element array  127  through the terminal φi. 
     The start signal input through the terminal φi of the control driver  110  is input to the transfer element array  126  through the voltage drop element  128 . The voltage drop element  128  reduces the voltage of an input signal. 
     A start signal input terminal (terminal φs) of the transfer element array  126  and an on-signal input terminal (terminal φi) of the light-emitting element array  127  may be connected to an output terminal (terminal φi) of the control driver  110 . Thus, the signal (φi signal) output from the control driver  110  may be input simultaneously to the transfer element array  126  and the light-emitting element array  127 . Thus, the start signal input terminal (terminal φs) of the transfer element array  126  and the control driver  110  are not connected by a separate wire. 
     The transfer element array  126  includes a plurality of transfer elements, and the light-emitting element array  127  includes a plurality of light-emitting elements. The transfer elements may be controlled by a start signal and transfer signals (φ 1  and φ 2  signals). The light-emitting element array  127  may be turned on according to the state of the transfer element and the on signal. 
     The control driver  110  applies a start signal having a higher voltage than a high-level voltage of a transfer signal for controlling the on/off of the transfer elements. The start signal may be applied only once. 
     The transfer signal may have two alternate potentials. When a first voltage is a high-level voltage, a second voltage is a low-level voltage. 
     The start signal may have a higher level than the first voltage. The voltage level of the start signal may be determined according to the type and characteristics of the voltage drop element  128 . 
       FIG. 5  is an exemplary block diagram of a light-emitting element array module  500  according to an embodiment. As illustrated in  FIG. 5 , a voltage drop element  128  is connected between a terminal φs of the light-emitting element array chip  125  and a terminal φi of the light-emitting element array chip  525 . The voltage drop element  128  may be connected inside the light-emitting element array chip  525 . Thus, a signal received through the terminal φi of the light-emitting element array chip  525  may be applied to the light-emitting element array  127  and the voltage drop element  128 . 
       FIG. 6  is an exemplary block diagram of a light-emitting element array module  600  according to an embodiment. As illustrated in  FIG. 6 , a voltage drop element  128  is connected between a terminal φi of the control driver  110  and a terminal φs of the light-emitting element array chip  125 .  FIG. 6  illustrates a case where the voltage drop element  128  is connected outside the light-emitting element array chip  625 . 
       FIG. 7  is a diagram illustrating an example of the light-emitting element array chip  725  according to an embodiment. As illustrated in  FIG. 7 , the light-emitting element array chip  725  uses a diode as a voltage drop element. 
     The light-emitting element array chip  725  includes two diodes Ds and Ds 1  that that may be connected in a forward direction. When the diodes Ds and Ds 1  are connected in a forward direction and a voltage of a predetermined level or more is applied to the terminal φi, a current flows through the diodes Ds and Ds 1 . Since a voltage of a signal having passed through the diodes Ds and Ds 1  is reduced, a voltage of the terminal φs is lower than a voltage of the terminal φi. The voltage of the terminal φs is sufficient to operate the transfer element. A level of the voltage of the start signal is determined by a voltage drop level of the diodes Ds and Ds 1 . 
     A start signal and an on signal are input to the terminal φi of the light-emitting element array chip  125 . The level of the voltage of the start signal is higher than the maximum level of the voltage of the on signal. Thus, before the start signal is input to the light-emitting element array chip  125 , the transfer element or the light-emitting elements do not operate. 
     The diode connected in a forward direction may be connected between the start signal input terminal (terminal φs) of the transfer element array and the on-signal input terminal (terminal φi) of the light-emitting element array. The diodes may be connected as illustrated in  FIGS. 4 and 5 . While two diodes Ds and Ds 1  are illustrated in  FIG. 7 , one diode or three or more diodes may be used. 
     Operations of the transfer elements and the light-emitting elements are disclosed. 
     The light-emitting element array includes a plurality of light-emitting thyristors, and the transfer element array includes a plurality of transfer thyristors. In other words, the light-emitting elements may be light-emitting thyristors, and the transfer elements may be transfer thyristors. 
     The thyristor has a PNPN junction and includes a gate.  FIG. 7  illustrates a case where 256 thyristors are included on one light-emitting element array chip  725 , and G 1  and G 256  respectively denote gate terminals of the thyristors. When a voltage of a predetermined level or more is applied to a gate of the thyristor, since a breakdown voltage of the thyristor is lowered, an operation voltage of the thyristor is lowered. Thus, by applying a voltage to the gate of the thyristor, the thyristor may be operated by a lower driving voltage. 
     The start signal supplies a voltage to a gate G 1  of a transfer thyristor T 1 . The start signal is supplied to the gate G 1  through the diodes Ds 1  and Ds. The start signal has a voltage level that may operate the transfer thyristor T 1  even after a voltage drop. After passing through the diodes Ds 1  and Ds, due to a voltage drop, the on signal fails to have a voltage level that may operate the transfer thyristor T 1 . Thus, at an initial state, only the start signal may enable the transfer thyristors T 1  to T 256  to be in an operating state. Thereafter, the transfer thyristors T 1  to T 256  sequentially enter an operating state according to the transfer signal. 
     The transfer thyristor enters an operating state by the transfer signals (φ 1  signal and φ 2  signal). When the start signal is applied to the gate G 1  of the transfer thyristor T 1  and the transfer signal (φ 1  signal) is applied to the transfer thyristor T 1 , the transfer thyristor T 1  enters an operating state. 
     When the transfer thyristor T 1  is in an operating state, the light-emitting thyristor L 1  enters a light-emitting state. The gate G 1  of the transfer thyristor T 1  is equal to the gate of the light-emitting thyristor L 1 . Thus, when the transfer thyristor T 1  enters an operating state, the light-emitting thyristor L 1  also enters an operating state. When the light-emitting thyristor L 1  is in an operating state, the light-emitting thyristor L 1  emits light according to the on signal input through the terminal φi. 
     By repetition of the process, the transfer thyristors T 1  to T 256  sequentially enter an operating state, the light-emitting thyristors L 1  to L 256  enter an operating state, and the light-emitting thyristors sequentially emit light or do not emit light. 
       FIG. 8  is a diagram illustrating an example of the light-emitting element array chip  825  according to an embodiment. As illustrated in  FIG. 8 , the light-emitting element array chip  825  uses a Zener diode as a voltage drop element. 
     The light-emitting element array chip  825  includes Zener diodes Ds that are connected in a reverse direction. When the Zener diodes Ds are connected in a reverse direction and a voltage of a predetermined level or more is applied to the terminal φi, a current flows through the Zener diodes Ds. Since a voltage of a signal having passed through the Zener diode Ds is reduced, a voltage of the terminal φs is lower than a voltage of the terminal φi. Thus, a voltage level of the start signal is determined by a level of a breakdown voltage of the Zener diode Ds. 
     The Zener diode Ds connected in a reverse direction may be connected between the start signal input terminal (terminal φs) of the transfer element array and the on-signal input terminal (terminal φi) of the light-emitting element array. The Zener diodes may be connected as illustrated in  FIGS. 4 and 5 . While one Zener diode Ds is illustrated in  FIG. 8 , two or more Zener diodes Ds may be used. 
       FIG. 9  is a diagram illustrating an example of the light-emitting element array chip  925  according to an embodiment. As illustrated in  FIG. 9 , the light-emitting element array chip  925  uses a resistor as a voltage drop element. 
     The light-emitting element array chip  925  includes at least one resistor R. When a voltage of a predetermined level or more is applied to the terminal φi, a current flows through the resistor R. Since a voltage of a signal having passed through the resistor R is reduced, a voltage of the terminal φs is lower than a voltage of the terminal φi. Thus, a voltage level of the start signal is determined by a resistance value of the resistor R. 
     The resistor R may be connected between the start signal input terminal (terminal φs) of the transfer element array and the on-signal input terminal (terminal φi) of the light-emitting element array. The resistor R may be connected as illustrated in  FIGS. 4 and 5 . While one resistor R is illustrated in  FIG. 9 , two or more resistors may be used. 
     While  FIGS. 7 to 9  illustrate a diode, a Zener diode, or a resistor as a voltage drop element, a combination of at least two of a diode, a Zener diode, and a resistor may be used as a voltage drop element. When two or more different elements are used as a voltage drop element, a voltage level of the start signal may be determined according to a level of a voltage drop caused by the two or more different elements. 
       FIG. 10  is an exemplary timing diagram of signals output from a control driver. 
     As illustrated in  FIG. 10 , the control driver outputs a start signal φs and an on signal φi through one terminal. The start signal φs is output before the on signal φi and has a voltage level higher than a maximum value of the on signal φi. 
     A first transfer signal φ 1  may be applied to the odd-numbered transfer thyristors, and a second transfer signal φ 2  may be applied to the even-numbered transfer thyristors. 
     The first transfer signal φ 1  and the second transfer signal φ 2  have two potentials of a high level and a low level and alternately enter a high state and a low state. The first transfer signal φ 1  and the second transfer signal φ 2  overlap with each other for a time ta. This is to allow the next transfer thyristor to enter a standby state before an operation of the previous transfer thyristor is ended. A time tb is a time predetermined for stable operation of the light-emitting element, and a time tw is a time when the light-emitting element actually operates. 
     When the start signal φs is input, the first transfer signal φ 1  enters a low state and the first transfer thyristor T 1  is turned on. The control driver  110  turns on the first light-emitting thyristor L 1  by using the on signal φi. Thereafter, when the first transfer signal φ 1  enters a high state and the second transfer signal φ 2  enters a low state, the control driver  110  turns on the second light-emitting thyristor L 2  by using the on signal φi. By repetition of the process, the control driver  110  may turn on the first to 256th light-emitting thyristors L 1  to L 256 . 
       FIG. 11  is an exemplary timing diagram of signals output from a control driver. As illustrated in  FIG. 11 , the control driver may sequentially turn on the light-emitting thyristors included in a light-emitting element array chip by applying the start signal once by performing a temporary switching operation. The control driver may sequentially turn on the light-emitting thyristors by applying the start signal again after the turn-on of all the light-emitting thyristors is ended. 
       FIG. 12  is a diagram illustrating a method of transferring the start signal and the data signal. As illustrated in  FIG. 12 , the control driver  1210  further includes a data transfer unit  111  and a start signal generating unit  112 . 
     The data transfer unit  111  outputs a data signal φ′I indicating the on/off of the light-emitting elements, and the start signal generating unit  112  outputs a start signal φs for operating the transfer elements. 
     By using a switch  113 , the control driver  110  outputs the start signal φs and the data signal φ′i to the terminal φi. By performing a switching operation, the control driver  110  connects the start signal generating unit  112  and the terminal φi to output the start signal φs and connects the data transfer unit  111  and the terminal φi to output the data signal φi. 
       FIG. 13  is a flowchart of a method of controlling a light-emitting element array chip according to an embodiment. 
     In operation  1310 , the control driver, e.g., control driver  110  receives print data. The print data may be received from the CPU or the PC  50 . The print data is data about an image that is to be printed by the image forming apparatus. 
     In operation  1320 , the control driver, e.g., control driver  110  controls the light-emitting element array chips e.g., light-emitting array chips  125  based on the print data. The control driver  110  applies a start signal to the transfer element array  126  by using a signal applied to the light-emitting element array  127  of the light-emitting element array chips  125 . 
     The control driver  110  controls an operation point of the light-emitting element array chips  125  by separately applying a start signal to the light-emitting element array chips  125 . The chip array  120  includes a plurality of light-emitting element array chips  125 . The control driver  110  may apply the start signal to the light-emitting element array chips  125  at different points. 
     The control driver  110  corrects a registration error in the main scanning direction of the light-emitting element array chips  125  by controlling a timing to apply the start signal to the light-emitting element array chips  125  according to the registration error. A registration error exists between the light-emitting element array chips  125 , and the control driver  110  controls an operation point of the light-emitting element array chips  125  in order to correct the registration error. In other words, the control driver  110  corrects an image in the main scanning direction by controlling an exposure timing by controlling a timing of the start signal input to the light-emitting element array chips  125 . 
     The control driver  110  applies a start signal having a higher voltage than a high-level voltage of a transfer signal for controlling the on/off of the transfer elements. In order to turn on/off the transfer elements, the control driver  110  applies a high-voltage or low-voltage transfer signal to the transfer elements. The start signal has a higher voltage than a high-level voltage of the transfer signal, and the transfer elements start operating when the start signal is applied to the transfer elements. 
     The control driver  110  transfers a data signal indicating an image to the light-emitting element array  127 . The data signal indicates the on/off of the light-emitting elements. 
     According to the one or more embodiments, since both the start signal receiving terminal and the data signal receiving terminal of the light-emitting element array chip are connected to the on-signal output terminal of the control driver, the number of wire bondings in the light-emitting array module may be reduced. 
     According to an exemplary method of controlling the light-emitting element array chips, the light-emitting element array chips may be separately controlled by controlling the point when the start signal is output to each of the light-emitting element array chips. 
     According to an exemplary method of controlling the light-emitting element array chips, the registration error of the light-emitting element array chips may be corrected by separately controlling the light-emitting element array chips. 
     According to an exemplary method of controlling the light-emitting element array chips, when the image corresponding to the light-emitting element array chip is all white, the start signal is not output to the light-emitting element array chip and thus the transfer element array is not driven, thereby making it possible to reduce power consumption caused by the driving of the light-emitting element array chip. 
     The apparatuses according to an exemplary embodiment may include a processor, a memory for storing and executing program data, a permanent storage such as a disk drive, a communication port for communicating with an external device, and user interface (UI) devices such as a touch panel, keys, and buttons. Methods implemented by a software module or algorithm may be stored on a non-transitory computer-readable recording medium as computer-readable codes or program commands that are executable on the processor. Examples of the computer-readable recording medium include magnetic storage media (e.g., read-only memories (ROMs), random-access memories (RAMs), floppy disks, and hard disks) and optical recording media (e.g., compact disk-read only memories (CD-ROMs) and digital versatile disks (DVDs)). The computer-readable recording medium may also be distributed over network-coupled computer systems so that the computer-readable codes may be stored and executed in a distributed fashion. The computer-readable recording medium is readable by a computer, and may be stored in a memory and executed in a processor. 
     The embodiments may be described in terms of functional block components and various processing operations. An exemplary functional block may be implemented by hardware and/or software components. For example, an exemplary embodiments may employ various integrated circuit (IC) components, such as memory elements, processing elements, logic elements, and lookup tables, which may execute various functions under the control of one or more microprocessors or other control devices. An exemplary element elements may be implemented by software programming or software elements, and implemented by a programming or scripting language such as C, C++, Java, or assembly language, with various algorithms being implemented by a combination of data structures, processes, routines, or other programming elements. An exemplary functional aspect may be implemented by an algorithm that is executed in one or more processors. An exemplary “mechanism,” “element,” “unit,” and “configuration” are not limited to mechanical and physical configurations, and may include software routines in conjunction with processors or the like. 
     Particular implementations described herein are merely exemplary, and do not limit the scope of the present invention. Connection lines or connection members illustrated in the drawings represent exemplary functional connections and/or physical or logical connections between the various elements, and various alternative or additional functional connections, physical connections, or logical connections may used. 
     The use of the terms “a,” “an,” and “the” and similar referents in the context of the specification (especially in the context of the following claims) may be construed to cover both the singular and the plural. Also, recitation of a range of values herein refer individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. The operations of the method described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by the context. The scope of the present invention is not limited to the above-described operation order. Examples or exemplary terms (e.g., “such as”) provided herein are used to describe the embodiments in detail, and the scope is not limited by the examples or exemplary terms unless otherwise claimed. Also, those of ordinary skill in the art will readily understand that various modifications and combinations may be made according to design conditions and factors without departing from the spirit and scope of the present invention as defined by the following claims. 
     It should be understood that the exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
     While one or more embodiments of the present invention have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.