Image forming apparatus, non-transitory recording medium storing paper-information obtaining program, and paper-information obtaining method

A non-transitory recording medium storing a computer-readable program for obtaining paper information in a system including an image forming apparatus, the image forming apparatus including:

• a print engine that forms an image on a sheet;
• a sheet conveyer that conveys a sheet on which the print engine formed an image, along a sheet path;
• at least one reflection-type optical sensor that measures a sheet in the sheet path;
• and
• at least one backing, facing the at least one reflection-type optical sensor across the sheet path, configured to change optical density of a backing face which is to be placed under a sheet in the sheet path for a measurement of the sheet with each of the at least one reflection-type optical sensor,
• the program comprising instructions which, when executed by a hardware processor in the system, cause the hardware processor to perform operations comprising:
• controlling the optical density of the backing face for each measurement of a sheet in the sheet path;
• causing the at least one reflection-type optical sensor to take measurements of the sheet in the sheet path by using different optical densities of the backing face;
• and
• calculating paper weight, which is weight of paper per unit area, of the sheet on a basis of a result of the measurements.

A method of obtaining paper information in a system including an image forming apparatus, the image forming apparatus including:

• a print engine that forms an image on a sheet;
• a sheet conveyer that conveys a sheet on which the print engine formed an image, along a sheet path;
• at least one reflection-type optical sensor that measures a sheet in the sheet path;
• and
• at least one backing, facing the at least one reflection-type optical sensor across the sheet path, configured to change optical density of a backing face which is to be placed under a sheet in the sheet path for a measurement of the sheet with each of the at least one reflection-type optical sensor,
• the method comprising:
• controlling the optical density of the backing face for each measurement of a sheet in the sheet path;
• causing the at least one reflection-type optical sensor to take measurements of the sheet in the sheet path by using different optical densities of the backing face;
• and
• calculating paper weight, which is weight of paper per unit area, of the sheet on a basis of a result of the measurements.