Optical device capable of minimizing output variation due to feedback light, optical scanning apparatus, and image forming apparatus

An optical device comprising:

• a surface-emitting laser array having a plurality of light-emitting portions;
• a package member on which the surface-emitting laser array is disposed;
• and
• a transparent member retained on the package member and disposed on an optical path of a light beam emitted by the surface-emitting laser array,
• the transparent member including an incident plane on which the light beam emitted by the surface-emitting laser array is incident,
• each light-emitting portion amongst the plurality of light-emitting portions including an upper reflector layer and a lower reflector layer, a combination of the upper reflector layer and lower reflector layer of the light-emitting portion defining a resonator,
• wherein light reflected back from the transparent member is incident upon an upper surface of the resonator,
• wherein the incident plane of the transparent member is inclined with respect to an emitting surface of the surface-emitting laser array at a first inclination angle which is smaller than or equal to a second inclination angle at which the light emitted by one of the light-emitting portions is incident on another of the light-emitting portions via reflection by the transparent member,
• wherein the one of the light emitting portions and said another of the light emitting portions are spaced apart from each other by the greatest distance among the light emitting portions of the surface-emitting laser array, and
• wherein the first inclination angle of the transparent member is set such that total reflectivity of the feedback light incident on the resonator of said another of the light emitting portions is at least 99% of the incident light.