# US 11,310,394 B2 · Image forming apparatus, image forming method, and computer-readable non-transitory recording medium storing image forming program, for performing color cailibration by using reference > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,310,394 B2 - Document ID: US11310394B2 - Status: Granted - Kind: B2 - Application number: 17/105,701 - Filed: 2020-11-27 - Published: 2021-05-27 - Granted: 2022-04-19 - Earliest claimed: 2019-11-27 - Assignees: KYOCERA Document Solutions Inc. - Applicants: KYOCERA Document Solutions Inc. - Inventors: Kenichi Hayashi - Web page: https://patentgrep.com/patent/US11310394B2 ## CPC - H04N 1/60: Colour correction or control {(H04N1/54 takes precedence)} - H04N 1/00045: {using a reference pattern designed for the purpose, e.g. a test chart} - H04N 1/00087: {Setting or calibrating (picture signal circuits H04N1/40)} - H04N 1/6033: {using test pattern analysis (H04N1/6055 takes precedence)} - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An image forming apparatus can perform color calibration by using a reference document generated with use of ink and an external colorimeter. An image reading unit reads an image on a document and generates image data. An image forming unit forms an image on an image forming medium by using CMY toners. A color calibration processing unit sets a correction coefficient by using a spectral reflectance of the reference document in a visible band, and a spectral reflectance in the visible band of a toner image formed on the image forming medium with use of toner. The color calibration processing unit also performs correction by multiplying the correction coefficient with a gradation value of each of RGB, generates a conversion formula from the each gradation value of RGB to each device-independent value, and generates a color profile by using the conversion formula. ## Claims ### Claim 1 An image forming apparatus configured to perform color calibration by using a reference document generated with use of a plurality of inks including CMY inks as a first color material, and an external colorimeter, and form an image on an image forming medium by using a plurality of toners including CMY toners as a second color material, comprising: an image sensor that reads an image on a document and generates image data; and a controller that sets a correction coefficient for bringing a color of the reference document and a color of a toner image close to each other by using a first spectral reflectance of the reference document in a visible band and a second spectral reflectance in the visible band of the toner image formed on the image forming medium with use of the toner, performs correction by multiplying the correction coefficient with a gradation value of each of RGB acquired by reading the reference document by the image sensor, generates a conversion formula from the each acquired gradation value of RGB to each device-independent value by using the each corrected gradation value of RGB, and the each device-independent value acquired by measuring the reference document with use of the external colorimeter, and generates a color profile by using the conversion formula. ### Claim 2 (depends on 1) The image forming apparatus according to claim 1, wherein the controller determines the correction coefficient by using a ratio between a cumulative value of the first spectral reflectance of the reference document in a visible band, and a cumulative value of the second spectral reflectance of the toner image in the visible band. ### Claim 3 (depends on 1) The image forming apparatus according to claim 1, wherein the controller calculates a third spectral reflectance for reproducing a device-independent value in terms of the toner image by calculating the device-independent value acquired by using the external colorimeter with use of a specific second-order or higher approximate conversion formula. ### Claim 4 (depends on 1) The image forming apparatus according to claim 1, wherein the reference document is generated by offset printing with use of ink as the first color material. ### Claim 5 An image forming method capable of performing color calibration by using a reference document generated with use of a plurality of inks including CMY inks as a first color material, and a colorimeter outside an image forming apparatus, comprising: reading an image on a document and generating image data; forming an image on an image forming medium by using a plurality of toners including CMY toners as a second color material; and setting a correction coefficient for bringing a color of the reference document and a color of a toner image close to each other by using a first spectral reflectance of the reference document in a visible band, and a second spectral reflectance in the visible band of the toner image formed on the image forming medium with use of the toner, performing correction by multiplying the correction coefficient with a gradation value of each of RGB acquired by reading the reference document in the image reading step, generating a conversion formula from the each acquired gradation value of RGB to each device-independent value with use of the each corrected gradation value of RGB, and the each device-independent value acquired by measuring the reference document with use of the external colorimeter, and generating a color profile by using the conversion formula. ### Claim 6 A computer-readable non-transitory recording medium storing an image forming program for controlling an image forming apparatus capable of performing color calibration by using a reference document generated with use of a plurality of inks including CMY inks as a first color material, and an external colorimeter, the image forming program causing the image forming apparatus to execute: reading an image on a document and generates image data; forming an image on an image forming medium by using a plurality of toners including CMY toners as a second color material; and setting a correction coefficient for bringing a color of the reference document and a color of a toner image close to each other by using a first spectral reflectance of the reference document in a visible band, and a second spectral reflectance in the visible band of the toner image formed on the image forming medium with use of the toner, performing correction by multiplying the correction coefficient with a gradation value of each of RGB acquired by reading the reference document, generating a conversion formula from the each acquired gradation value of RGB to each device-independent value by using the each corrected gradation value of RGB, and the each device-independent value acquired by measuring the reference document with use of the external colorimeter, and generating a color profile by using the conversion formula.