Image forming apparatus, image processing apparatus and image forming method

1. An image forming apparatus comprising:

a first toner image forming section that forms a visible toner image;

a second toner image forming section that forms an invisible toner image, a resolution of the invisible toner image is lower than a resolution of the visible toner image; and

a transfer section that transfers to a medium the visible toner image and the invisible toner image;

wherein the resolution of the visible toner image in a main scanning direction is higher than the resolution of the invisible toner image in the main scanning direction,

wherein the first toner image forming section and the second toner image forming section include a first scanning section and a second scanning section scanning a laser light on a photoreceptor, respectively, and the first scanning section and the second scanning section are configured to satisfy the following relation:

Fv/Vv>Fi/Vi

where Fv and Fi are a laser light modulation frequency in the first scanning section and the second scanning section, respectively, and Vv and Vi are a scanning speed of the first scanning section and the second scanning section, respectively.

2. The image forming apparatus according to claim 1 , wherein each of the first scanning section and the second scanning section includes a light source comprising a surface emitting laser array.

3. The image forming apparatus according to claim 1 , wherein an infrared light absorptance of a colorant used in the first toner image forming section is lower than an infrared light absorptance of a colorant used in the second toner image forming section.

4. The image forming apparatus according to claim 1 , wherein the resolution of the visible toner image in a sub-scanning direction is higher than the resolution of the invisible toner image in the sub-scanning direction.

5. The image forming apparatus according to claim 4 , wherein the first toner image forming section and the second toner image forming section include a first scanning section and a second scanning section scanning a laser light on a photoreceptor, respectively, and the first scanning section and the second scanning section are configured to satisfy the following relation:

Nv×Vv>Ni×Vi

where Nv and Ni are the number of laser lights scanned by the first scanning section and the second scanning section, respectively, and Vv and Vi are the scanning speed of the first scanning section and the second scanning section, respectively.

6. The image forming apparatus according to claim 5 , wherein each of the first scanning section and the second scanning section includes a light source comprising a surface emitting laser array.

7. An image forming apparatus comprising:

a first toner image forming section that forms a visible toner image;

a second toner image forming section that forms an invisible toner image;

a first correction section that corrects a position of the visible toner image at a first correction interval; and

a second correction section that corrects a position of the invisible toner image at a second correction interval longer than the first correction interval.

8. An image forming method comprising:

forming a visible toner image in a first resolution;

forming an invisible toner image in a second resolution which is lower than the first resolution; and

transferring the visible toner image and the invisible toner image onto the medium;

further comprising, before forming the visible toner image and the invisible toner image:

generating image data which is the base of the visible image in a third resolution; and

generating image data which is the base of the invisible image in a fourth resolution which is lower than the third resolution.

9. An image forming method comprising:

forming a visible toner image;

forming an invisible toner image;

correcting a position of the visible toner image at a first correction interval; and

correcting a position of the invisible toner image at a second correction interval longer than the first correction interval.