Image forming apparatus, method for forming image, and computer-readable recording medium

1. An image forming apparatus comprising:

an image bearing member configured to bear an image;

a transfer member to which the image can be transferred from the image bearing member;

a correction-image-formation control unit configured such that, on the transfer member, a bias correction image is formed based on an uncorrected bias and a first parameter-correction image is formed behind the bias correction image based on the uncorrected bias and an uncorrected image-formation parameter with no intervening correction image;

a bias correcting unit configured to obtain a corrected bias by correcting the uncorrected bias based on the bias correction image;

a bias determining unit configured to determine whether the corrected bias is within a predetermined range defined based on the uncorrected bias;

a parameter correcting unit configured to obtain, if the corrected bias is within the predetermined range, a corrected image-formation parameter by correcting the uncorrected image-formation parameter based on the first parameter-correction image; and

wherein if the corrected bias is outside the predetermined range, the correction-image-formation control unit causes a second parameter-correction image to be formed after the first parameter-correction image based on the corrected bias and the uncorrected image-formation parameter, and the parameter correcting unit obtains a corrected image-formation parameter by correcting the uncorrected image-formation parameter based on the second parameter-correction image.

2. The image forming apparatus according to claim 1 , comprising:

an environmental-parameter obtaining unit configured to obtain an environmental parameter related to an environment around the transfer member;

a storage unit configured to store a table that associates the environmental parameter with a variation in the bias; and

wherein the correction-image-formation control unit causes the first parameter-correction image to be formed based on the environmental parameter obtained by the environmental-parameter obtaining unit and the variation corresponding to the obtained environmental parameter.

3. The image forming apparatus according to claim 2 , wherein the storage unit updates the table based on the corrected bias.

4. The image forming apparatus according to claim 2 , wherein the storage unit stores the temperature around the transfer member as the environmental parameter.

5. The image forming apparatus according to claim 2 , wherein the storage unit stores the humidity around the transfer member as the environmental parameter.

6. The image forming apparatus according to claim 1 , wherein the image-formation parameter is a .gamma. table.

7. A method for forming an image comprising:

causing a bias correction image to be formed on a transfer member to which an image is transferred from an image bearing member bearing the image based on an uncorrected bias and a first parameter-correction image to be formed behind the bias correction image based on the uncorrected bias and an uncorrected image-formation parameter with no intervening correction image;

obtaining a corrected bias by correcting the uncorrected bias using the bias correction image;

determining whether the corrected bias is within a predetermined range defined based on the uncorrected bias;

obtaining, if the corrected bias is within the predetermined range, a corrected image-formation parameter by correcting the uncorrected image-formation parameter using the first parameter-correction image; and

wherein if the corrected bias is outside the predetermined range, a second parameter-correction image is formed after the first parameter-correction image based on the corrected bias and the uncorrected image-formation parameter, and a corrected image-formation parameter is obtained by correcting the uncorrected image-formation parameter based on the second parameter-correction image.

8. A non-transitory computer-readable recording medium recording a program for having a computer function as:

a correction-image-formation control unit configured so as to cause, on a transfer member to which an image is transferred from an image bearing member bearing the image, a bias correction image to be formed based on an uncorrected bias and a first parameter-correction image to be formed behind the bias correction image based on the uncorrected bias and an uncorrected image-formation parameter with no intervening correction image;

a bias correcting unit configured to obtain a corrected bias by correcting the uncorrected bias based on the bias correction image;

a bias determining unit configured to determine whether the corrected bias is within a predetermined range defined based on the uncorrected bias;

a parameter correcting unit configured to obtain, if the corrected bias is within the predetermined range, a corrected image-formation parameter by correcting the uncorrected image-formation parameter based on the first parameter-correction image; and

wherein if the corrected bias is outside the predetermined range, the correction-image-formation control unit causes a second parameter-correction image to be formed after the first parameter-correction image based on the corrected bias and the uncorrected image-formation parameter, and the parameter correcting unit obtains a corrected image-formation parameter by correcting the uncorrected image-formation parameter based on the second parameter-correction image.