Image reading apparatus and image forming apparatus

摘要

An image reading apparatus include a light source; an image sensor configured to output an image signal of an object illuminated by the light source; a first calculating unit configured to calculate a third light amount based on a difference between a first image signal output from the image sensor when the light source illuminates a reference member as the object at a first light quantity and a second image signal output from the image sensor when the light source illuminates the reference member at a second light quantity and a difference between the first light quantity and the second light quantity; and a light quantity setting unit configured to set a light quantity at which the light source illuminates a document as the object to the third light quantity.

主权项

1. An image reading apparatus comprising:
a light source; an image sensor configured to output an image signal of an object illuminated by the light source; a first calculating unit configured to calculate a third light amount based on a difference between a first image signal output from the image sensor when the light source illuminates a reference member as the object at a first light quantity and a second image signal output from the image sensor when the light source illuminates the reference member at a second light quantity and a difference between the first light quantity and the second light quantity; and a light quantity setting unit configured to set a light quantity at which the light source illuminates a document as the object to the third light quantity, wherein the first calculating unit calculates the third light quantity based on a difference between a peak value of the first image signal and a peak value of the second image signal and the difference between the first light quantity and the second light quantity, and wherein the first calculating unit divides the difference between the peak value of the first image signal and the peak value of the second image signal by the difference between the first light quantity and the second light quantity to obtain a variation in an image signal per unit of light quantity variation, divides a difference between the peak value of the first image signal or the peak value of the second image signal and a predetermined target value by the variation in the image signal per unit of light quantity variation to obtain a necessary light quantity variation such that the peak value of the first image signal or the peak value of the second image signal becomes the target value, and adds the light quantity variation thus obtained to the first light quantity or the second light quantity to calculate the third light quantity.