IMAGE FORMING APPARATUS

Abstract

In an image forming apparatus which expresses lamp lighting energy corresponding to input gray scale data on the basis of on/off of lighting lamp of plural sub-dots corresponding to different lamp lighting times of different assistant scanning positions, with respect to such image that rapidly changes from a state close to white level toward a state close to black level, or with respect to such image that rapidly changes from a state close to black level toward a state close to white level, in order to decrease that a thin white stripe or a thin black stripe happens on the border portion, a random generator 34 and a adding circuit 33 are provided so that: whenever the gray scale value is inputted to the gray scale value input register 31, with respect to the lamp lighting energy, a random number of predetermined level is added.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a summary diagram showing a LED printer;

FIG. 2 is a block diagram showing a print controlling section and a structure of LED head of embodiment 1;

FIG. 3 is a transformation table of standardization exposure energy and sub-dot data;

FIG. 4 is a time chart of LED printer of embodiment 1;

FIG. 5 is a diagram showing an output of random number generator;

FIG. 6 is an explanation diagram for explaining a gray scale pixel forming method of embodiment 1;

FIG. 7 is a block diagram showing a print controlling section and a structure of LED head of embodiment 2;

FIG. 8 is an explanation diagram of a modulation control selecting table;

FIG. 9 is a time chart of LED printer of embodiment 2;

FIG. 10 is an explanation diagram of inputted gray scale value (second);

FIG. 11 is an explanation diagram for explaining a gray scale pixel forming method of embodiment 2;

FIG. 12 is an explanation diagram of inputted gray scale value (first);

FIG. 13 is an explanation diagram showing a relation between gray scale value and standardization exposure energy of each pixel; and

FIG. 14 is an explanation diagram for explaining a conventional gray scale pixel forming method.

Claims

1. An image forming apparatus which expresses lamp lighting energy corresponding to gray scale data on the basis of on/off of lighting lamp of plural dots corresponding to different lamp lighting times of respective different scanning positions, comprising: a random number modulation controlling section which, with respect to a lamp lighting energy, executes a random number addition calculation of predetermined level whenever said gray scale data is inputted.

2. The image forming apparatus according to claim 1, further comprising: a modulation control selecting section which, with respect to a composed center position of said lamp lighting energy in plural said dots and a predetermined ideal center position, compares their difference quantities before and after said random number addition calculation, if said difference quantity after said random number addition calculation is bigger than said difference quantity before said random number addition calculation, stops said random number modulation controlling section to operate.

3. The image forming apparatus according to claim 2, wherein said modulation control selecting section previously has random number modulation control information as a judgment standard to judge whether said difference quantity after said random number addition calculation is bigger than said difference quantity before said random number addition calculation, per gray scale value of said inputted gray scale data.

4. The image forming apparatus according to claim 1, wherein said predetermined level corresponds to said on/off of one dot whose lamp lighting time is shortest in said different lamp lighting times of respective different scanning positions.

5. The image forming apparatus according to claim 4, wherein said random number modulation controlling section has a random generator to respectively generate 1 or 0 in a predetermined cycle and a probability of ½.

6. The image forming apparatus according to claim 4, further comprising: a modulation control selecting section which, with respect to a composed center position of said lamp lighting energy in plural said dots and a predetermined ideal center position, compares their difference quantities before and after said random number addition calculation, if said difference quantity after said random number addition calculation is bigger than said difference quantity before said random number addition calculation, stops said random number modulation controlling section to operate.

7. The image forming apparatus according to claim 6, wherein said modulation control selecting section previously has random number modulation control information as a judgment standard to judge whether said difference quantity after said random number addition calculation is bigger than said difference quantity before said random number addition calculation, per gray scale value of said inputted gray scale data.

8. An image forming apparatus which executes a light emission control where light emitting elements emit light according to a plurality of gray scale data corresponding to an image, comprising: a random number calculation controlling section which executes a random number addition calculation of a predetermined range and performs an output per gray scale data; anda light emission controlling section which executes a light emission control of said light emitting elements according to said output of said random number calculation controlling section.

9. The image forming apparatus according to claim 8, wherein said predetermined range is a value which corresponds to a shortest lighting-lamp control time of said light emitting elements.

10. The image forming apparatus according to claim 8, wherein said random number calculation controlling section adds a value of said predetermined range in a probability of ½.

11. The image forming apparatus according to claim 8, further comprising: a calculation control selecting section which, when said random number calculation controlling section executes a random number addition calculation with respect to said gray scale data in said predetermined range, if detected that said gray scale data before said random number addition calculation is not in a concentration range previously stored, makes said random number calculation controlling section output said gray scale data without executing said random number addition calculation.

12. The image forming apparatus according to claim 11, wherein said predetermined range is a range to indicate one of said plurality of gray scale data; said calculation control selecting section individually performs detection with respect to said plurality of gray scale data.

13. An image forming apparatus which executes a light emission control where LED elements that are arranged emit light according to a plurality of gray scale data corresponding to an image, and forms a gray scale image, comprising: a random number calculation controlling section which executes a random number addition calculation of a predetermined range and performs an output per gray scale data; anda light emission controlling section which executes a light emission control of said LED elements according to said output of said random number calculation controlling section.

14. The image forming apparatus according to claim 13, wherein said predetermined range is a value which corresponds to a shortest lighting-lamp control time of said LED elements.

15. The image forming apparatus according to claim 13, wherein said random number calculation controlling section adds a value of said predetermined range in a probability of ½.

16. The image forming apparatus according to claim 13, further comprising: a calculation control selecting section which, when said random number calculation controlling section executes a random number addition calculation with respect to said gray scale data in said predetermined range, if detected that said gray scale data before said random number addition calculation is not in a concentration range previously stored, makes said random number calculation controlling section output said gray scale data without executing said random number addition calculation.

17. The image forming apparatus according to claim 16, wherein said predetermined range is a range to indicate one of said plurality of gray scale data; said calculation control selecting section individually performs detection with respect to said plurality of gray scale data.