Image reading apparatus and image forming apparatus

An image reading apparatus comprising:

• a light emitter configured to irradiate a document with light;
• a first light guide configured to guide the light reflected by the document;
• an output device configured to output a readout signal obtained from the light reflected and guided by the first light guide;
• a base configured to correct shading in the readout signal;
• and
• circuitry configured to
• output a scanned image in which the shading of the document in the readout signal is corrected, based on correction data obtained from the readout signal of the base output from the output device,
• control a timing at which the light emitter emits the light and a timing at which the output device outputs a signal,
• heat the first light guide with the light emitted from the light emitter before the output device outputs the readout signal of each of the document and the base, and
• correct the shading in the readout signal of the document output from the output device when the first light guide is heated, based on the correction data obtained when the first light guide is heated.