Image forming apparatus

1. An image forming apparatus comprising:

a photoconductor;

an exposure device including a chip having a first light-emitting element array and a second light-emitting element array, the first light-emitting element array including a plurality of light-emitting elements disposed in a first direction that is parallel to a rotational axis direction of the photoconductor, the second light-emitting element array including a plurality of light-emitting elements disposed in the first direction, the first light-emitting element array and the second light-emitting element array being disposed sequentially in a second direction orthogonal to the first direction, the exposure device being configured to perform multiple exposure with the second light-emitting element array of an exposure position of the photoconductor exposed with the first light-emitting element array; and

a controller configured to transmit, to the exposure device, a signal for controlling the exposure device,

wherein the exposure device:

sets a first pulse signal for light emission of the first light-emitting element array, based on a first delay time from an input timing of a line synchronizing signal to a first start timing at which light emission starts and a first pulse width from the first start timing to a first termination timing at which the light emission terminates before a next input timing of the line synchronizing signal,

sets a second pulse signal for light emission of the second light-emitting element array, based on a second delay time, different from the first delay time, from the input timing of the line synchronizing signal to a second start timing at which light emission starts and a second pulse width, identical to the first pulse width, from the second start timing to a second termination timing at which the light emission terminates before the next input timing of the line synchronizing signal, and

starts and terminates light emission of each of the first light-emitting element array and the second light-emitting element array according to the set first pulse signal and second pulse signal.

2. The image forming apparatus according to claim 1 , wherein

when the first delay time and the first pulse width as set values for the first light-emitting element array are defined, respectively, as a0 and b0 and the second delay time and the second pulse width as set values for the second light-emitting element array are defined, respectively, as a1 and b1, the following expressions are satisfied: a0≠a1, b0=b1, and a0+b0≠a1+b1.

3. The image forming apparatus according to claim 1 , wherein

the exposure device includes a pulse signal generation portion configured to generate a pulse signal for light emission of a light-emitting element array, based on a delay time from an input timing of the line synchronizing signal to a start timing at which light emission starts and a pulse width from the start timing to a termination timing at which the light emission terminates, and

the pulse signal generation portion generates the first pulse signal for light emission of the first light-emitting element array, based on the first delay time from the input timing of the line synchronizing signal to the first start timing at which light emission starts and the first pulse width from the first start timing to a first termination timing at which the light emission terminates before the next input timing of the line synchronizing signal, and generates the second pulse signal for light emission of the second light-emitting element array, based on the second delay time, different from the first delay time, from the input timing of the line synchronizing signal to the second start timing at which light emission starts and the second pulse width, identical to the first pulse width, from the second start timing to a second termination timing at which the light emission terminates before the next input timing of the line synchronizing signal.

4. The image forming apparatus according to claim 1 , wherein

in a cycle of the line synchronizing signal in which the multiple exposure with the second light-emitting element array is performed on the exposure position exposed with the first light-emitting element array, the exposure device:

sets the second pulse signal for light emission of the second light-emitting element array based on the first delay time set for the first light-emitting element array in a previous cycle of the line synchronizing signal, and

sets the first pulse signal for light emission of the first light-emitting element array based on a delay time different from the first delay time set for the first light-emitting element array in the previous cycle of the line synchronizing signal.

5. The image forming apparatus according to claim 1 , wherein

the exposure device includes:

a delay time generation portion configured to generate a different delay time every cycle of the line synchronizing signal; and

a delay time storage portion configured to store a delay time set for a light-emitting element array, and wherein the exposure device:

sets the second pulse signal for light emission of the second light-emitting element array based on the first delay time set for the first light-emitting element array in a previous cycle of the line synchronizing signal, which is stored in the delay time storage portion, and

sets the first pulse signal for light emission of the first light-emitting element array based on a delay time different from the first delay time set for the first light-emitting element array in the previous cycle of the line synchronizing signal, which is generated by the delay time generation portion.

6. The image forming apparatus according to claim 5 , wherein

the delay time generation portion generates a different delay time every cycle of the line synchronizing signal with a pseudorandom number.