Patent ID: 8659791
Filing Date: 2014-02-25
Classification: H04N

Abstract:
1. An LED emission wavelength estimation method of estimating emission wavelengths of three LEDs which are mounted in an image reading apparatus to emit light of three primary colors, comprising: a test patch formation step of forming a test patch by printing on a printing medium using color materials; a first measurement of measuring a spectral reflectivity of the test patch formed on the printing medium using a spectroreflectometer; a second measurement of measuring emission wavelength characteristics of standard LEDs mounted in the image reading apparatus using a measuring device; a storage step of storing, into a memory, signal change characteristic data representing a relationship between signals corresponding to reflected light obtained by irradiating the test patch with the standard LEDs and a wavelength shift from a design wavelength of each of the standard LEDs, based on the spectral reflectivity measured in the first measurement step and the emission wavelength characteristics of the standard LEDs measured in the second measurement step; a patch formation step of forming a patch by printing on a printing medium using color materials; a reading step of reading the patch formed in the patch formation step, using the image reading apparatus including the memory and the three color LEDs; and an estimation step of estimating a wavelength shift from a design wavelength of each of the LEDs of the image reading apparatus, based on a signal obtained by reading the patch in the reading step and the signal change characteristic data stored in the memory.