All-dielectric film narrow band filter is widely used in laser system owing to its excellent optical capability,
manufacturability and environmental adaptability. But 905nm infrared semiconductor laser system have large divergence
angel so we designed entrance light cone angle 905nm narrow band filter. And center wavelength shift, due to entrance
light cone angle, affects its spectral selective power seriously. In order to reduce these impacts, an informal dielectric
film narrowband filter is designed. Changes of transmission characteristics with oblique incidence of Gaussian beam of
uneven illumination are analyzed. The relationship between the angle of incidence and the central wavelength shift
quantificational are Solved. A ± 30 ° incident 905nm narrowband filter was fabricated. Between 880nm and 950nm, the
average transmittance is above 90%, and at the cut-off band the average transmittance is below 1%.