Patent ID: 7313156

Claim:
A control method of controlling a distributed Bragg reflection (DBR) semiconductor laser in an image projecting apparatus, wherein the image projecting apparatus includes the DBR semiconductor laser which is provided with a phase region and a DBR region, a light wavelength converting device for converting fundamental-wave light emitted from the DBR semiconductor laser into second harmonic wave light, an optical deflector for scanning the second harmonic wave light in a one-dimensional or two-dimensional manner, and a modulating portion for modulating the DBR semiconductor laser based on an image signal, said control method comprising: a coefficient calculating step of calculating at least one coefficient in a relationship between a DBR current to be injected into the DBR region and a phase current to be injected into the phase region for continuously shifting the wavelength of the fundamental-wave light, within a non-drawing time during which a drawing signal, which corresponds to the image signal, is absent; and a wavelength adjusting step of changing the DBR current injected into the DBR region and the phase current injected into the phase region based on the relationship such that the second harmonic wave light is adjusted, within the non-drawing time, so as to stabilize the second harmonic wave light within a drawing time during which the drawing signal is present, wherein the second harmonic wave light is two-dimensionally deflected by the deflector in a relatively high-speed main scanning direction and a relatively low-speed auxiliary scanning direction, and wherein said coefficient calculating step is carried out in a vertical blanking time in the auxiliary scanning direction, and wherein said wavelength adjusting step is carried out in a horizontal blanking time in the main scanning direction.