Image reading apparatus having multiple wavelength light sources and control method for the same

Abstract

To keep operation of a control circuit for a line sensor reading operation always the same regardless of variations and differences between readers, simplify the control circuit, and avoid complicated processes such as setting various software process parameters for canceling differences between the readers. A line shaped, two-wavelength transmitting LED array and a line shaped light emitting/photodetecting part comprising a photodetector array and a two-wavelength reflecting LED array are disposed in opposition each other such that a read medium passes between the two-wavelength LED array for transmitting light and the light emitting/photodetecting part, and the two-wavelength LED array for tranmitting light and two-wavelength LED array for reflecting light emit light of different wavelengths. An storage time control circuit is disposed in a signal processing circuit of the photodetector array; and a control means is provided for controlling light emission with the two-wavelength transmitting LED array and two-wavelength reflecting LED array, controlling reading with the photodetectors, and controlling the storage time control circuit. Variations in wavelength detection sensitivity and light quantity with different scanned media are adjusted by means of the storage time of the storage time control circuit.