Patent ID: 7801192

Claim:
A monitoring method for monitoring an optical output from a VCSEL array in which a plurality of VCSELs are arranged on a substrate, comprising: causing a first VCSEL to emit light that is directed parallel to the substrate by changing a bias direction of a voltage applied to the first VCSEL to a forward direction; causing a second VCSEL to receive the light emitted from the first VCSEL and to convert the quantity of the light emitted from the first VCSEL into an electric signal by changing a bias direction of a voltage applied to the second VCSEL to a reverse direction; causing the second VCSEL to emit light in a direction parallel to the substrate by changing a bias direction of a voltage applied to the second VCSEL to a forward direction; and causing a third VCSEL to receive the light emitted from the second VCSEL and to convert the quantity of the light emitted from the second VCSEL into an electric signal by changing a bias direction of a voltage applied to the third VCSEL to a reverse direction.