Line head and image forming apparatus using the same

1. A line head, comprising:

a plurality of light emitting element columns, including:

a main light emitting element column, exposing a light amount necessary for exposure to an image carrier; and

an auxiliary light emitting element column, exposing the image carrier so as to obtain the light amount necessary for exposure even when a light emitting element having a pixel defect is existed in the main light emitting element column,

wherein the auxiliary light emitting element column has a plurality of light emitting elements which correspond to a plurality of light emitting elements of the main light emitting element column respectively; and

wherein the light emitting elements of the auxiliary light emitting element column respectively emit light to dots of an image region on the image carrier to which the corresponding light emitting elements of the main light emitting element column emit light.

2. A line head, comprising:

a plurality of light emitting element columns, including:

a main light emitting element column, exposing a light amount necessary for exposure to an image carrier; and

an auxiliary light emitting element column, exposing the image carrier so as to obtain the light amount necessary for exposure even when a light emitting element having a pixel defect is existed in the main light emitting element column,

wherein the auxiliary light emitting element column exposes the image carrier so that an amount of a change in differences between a surface potential Vs|V| and a developing bias potential Vd|V| of the image carrier in a case that the pixel defect is existed at the light emitting elements of the light emitting element columns and in a case that the pixel defect is not existed is equal to or smaller than 10%.

3. A line head, comprising:

a plurality of light emitting element columns, including:

a main light emitting element column, exposing a light amount necessary for exposure to an image carrier; and

an auxiliary light emitting element column, exposing the image carrier so as to obtain the light amount necessary for exposure even when a light emitting element having a pixel defect is existed in the main light emitting element column,

wherein at least one of a light attenuating characteristic (PIDC characteristic) of the image carrier and a light amount of the light emitting elements is set so that an amount of a change in differences between a surface potential Vs|V| and a developing bias potential Vd|V| of the image carrier in a case that the pixel defect is existed at the light emitting elements of the light emitting element columns and in a case that the pixel defect is not existed is equal to or smaller than 10%.

4. The line head as set forth in claim 3 , wherein the light emitting elements are organic EL elements.

5. An image forming apparatus, comprising:

a line head, comprising:

a plurality of light emitting element columns, including:

a main light emitting element column, exposing a light amount necessary for exposure to an image carrier; and

an auxiliary light emitting element column, exposing the image carrier so as to obtain the light amount necessary for exposure even when a light emitting element having a pixel defect is existed in the main light emitting element column;

an image carrier cartridge, to which the line head is mounted;

a charging unit, charging the image carrier;

a developing unit, developing a toner image on the image carrier; and

a transfer unit, transferring the toner image formed on the image carrier onto a transfer medium.

6. A line head, comprising:

a plurality of light emitting element columns, including:

a main light emitting element column, exposing an image carrier; and

an auxiliary light emitting element column, exposing the image carrier when a light emitting element having a pixel defect is existed in the main light emitting element column,

wherein when the light emitting element having the pixel defect is existed in the main light emitting element column, a light emitting of the main light emitting element column including the light emitting element having the pixel detect is stopped; and

wherein all of the light emitting elements of the auxiliary light emitting element column emit light.

7. The line head as set forth in claim 6 , wherein information regarding the main light emitting element column including the light emitting element having the pixel defect is stored in a storing member.

8. A line head. comprising:

a plurality of light emitting element columns, including:

a main light emitting element column, exposing an image carrier; and

an auxiliary light emitting element column, exposing the image carrier when a light emitting element having a pixel defect is existed in the main light emitting element column,

wherein when the light emitting element having the pixel defect is existed in the main light emitting element column, a light emitting of the light emitting element having the pixel detect is stopped; and

wherein a light emitting element of the auxiliary light emitting element column corresponding to the light emitting element having the pixel defect emits light so as to compensate a light emitting of the stopped light emitting element.

9. The line head as set forth in claim 8 , wherein information regarding a position of the light emitting element having the pixel defect in the main light emitting element column is stored in a storing member.

10. An image forming apparatus, comprising:

a line head, comprising:

a plurality of light emitting element columns, including:

a main light emitting element column, exposing an image carrier; and

an auxiliary light emitting element column, exposing the image carrier when a light emitting element having a pixel defect is existed in the main light emitting element column;

an image carrier cartridge, to which the line head is mounted;

a charging unit, charging the image carrier;

a developing unit, developing a toner image on the image carrier; and

a transfer unit, transferring the toner image formed on the image carrier onto a transfer medium.

11. The image forming apparatus as set forth in claim 10 , wherein the storing member is provided at the cartridge.

12. The image forming apparatus as set forth in claim 10 , wherein the storing member is provided on a main body side.

13. An image forming apparatus, comprising:

a line head, comprising:

a plurality of light emitting element columns, exposing an image carrier,

wherein when a light emitting element having the pixel defect is existed in one light emitting element column of the light emitting element columns, a light emitting of the light emitting element having the pixel detect is stopped; and

wherein a light emitting amount of a light emitting element in another light emitting element column of the light emitting element columns which corresponds to the light emitting element having the pixel defect is increased so as to compensate a light emitting of the stopped light emitting element;

an image carrier cartridge, to which the line head is mounted;

a charging unit, charging the image carrier;

a developing unit, developing a toner image on the image carrier; and

a transfer unit, transferring the toner image formed on the image carrier onto a transfer medium.

14. The image forming apparatus as set forth in claim 13 , wherein the storing member is provided at the cartridge.

15. The image forming apparatus as set forth in claim 13 , wherein the storing member is provided on a main body side.