Image forming apparatus that detects transition between patch images

An image forming apparatus comprising:

• an image forming unit configured to form a plurality of patch images in succession on a recording material;
• a detection unit configured to irradiate a patch image formed on the recording material with light, and detect light intensities at a plurality of wavelengths in the light reflected from the patch image;
• and
• a determination unit configured to determine that a patch image for which the detection unit is detecting light intensities has transitioned from a first patch image to a second patch image in a case where a light intensity at a plurality of wavelengths for identification of a patch image to be identified, the light intensity being detected by the detection unit, has varied by an amount greater than a first threshold corresponding to those plurality of wavelengths for identification,
• wherein the plurality of wavelengths for identification are commonly used for the patch images, and the plurality of wavelengths are selected from among wavelengths at which a light intensity in spectral distribution obtained by irradiating a white reference portion with light using a light source having a predetermined spectrum is greater than or equal to a second threshold, and
• the plurality of wavelengths are selected from among wavelengths corresponding to a local maximum value or a substantial local maximum value in the spectral distribution of the white reference portion.

An image forming apparatus comprising:

• an image forming unit configured to form a plurality of patch images in succession on a recording material;
• a detection unit configured to irradiate a patch image formed on the recording material with light, and detect light intensities at a plurality of wavelengths in the light reflected from the patch image;
• and
• a determination unit configured to determine that a patch image for which the detection unit is detecting light intensities has transitioned from a first patch image to a second patch image in a case where, after the light intensity at the wavelength has been detected for identification of the patch image to be identified, the light intensity being detected by the detection unit has varied by an amount greater than a first threshold corresponding to that wavelength for identification and it is detected that a variation in the light intensity at that wavelength for identification is less than or equal to a second threshold.

An image forming apparatus comprising:

• an image forming unit configured to form a plurality of patch images in succession on a recording material, the plurality of patch images being used for detecting tint;
• a spectral distribution detection unit configured to irradiate a patch image formed on the recording material with light, and disperse the light reflected from the patch image into a plurality of wavelengths;
• and
• a determination unit configured to determine that a patch image for which the spectral distribution detection unit is detecting is a first patch image or a second patch image among the plurality of patch images based on a intensity variation of a given wavelength among the plurality of wavelengths dispersed by the detection unit.