Inventors: Okamoto, Sota; Chikuma, Kiyofumi;
Assignee: Pioneer Electronic Corporation (Tokyo, JP)
Primary Examiner: Lee; John D.
Assistant Examiner: Heartney; Phan T.
Attorney, Agent or Firm: Fleit, Jacobson, Cohn, Price, Holman & Stern
A fibre-type light wavelength conversion device comprises a fibre-type wavelength conversion element for changing the wavelength of an incident light and a prismatic means for transforming said incident light, whose wavelength has been changed by said wavelength conversion element, into a parallel light, wherein said prismatic means is a Fresnel lens comprised of a plurality of concentric conical ring zones whose cross-section including its optical axis has a saw-tooth shape or comprised of a same pitch circular grating. Furthermore, a vertical angle of a surface of emergence of said conical ring zones is determined so as to satisfy the following equations of: sin x=n.sing y y+z=(.pi./2)-.alpha. cos .alpha.=n.sin z where x represents an angle of incidence of said incident light with respect to said optical axis of said Fresnel lens, n represents a refractive index of said Fresnel lens, y represents an angle of refraction at a surface of incidence, and z represents an angle of incidence into said surface of emergence. |
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