SCANNING TYPE PROJECTOR
A scanning type projector for scanning an optical beam emitted from a laser light source has a collimator lens and a scanning device. A beam demagnifying and shaping prism is disposed between the collimator lens and the scanning device. The cross section of the beam that is elliptical is demagnified along the major axis of the ellipse such that the cross section of the beam is shaped. Thus, the cross section of the beam fits within the effective diameter of a deflecting mirror incorporated in the scanning device. The optical beam is reflected efficiently. A bright image can be projected. The resolution is improved by the beam shaping effect.
1 . A scanning type projector for scanning an optical beam on a surface and projecting a two-dimensional image onto the surface, comprising:
at least one laser light source for emitting said optical beam in the form of divergent light;
at least one collimator lens for varying the optical beam into collimated light or converged light;
a scanning device for scanning the optical beam on said surface; and
an optical beam demagnifying and shaping device for demagnifying and shaping a cross section of the optical beam in a given direction of the cross section thereof.
2 . The scanning type projector according to claim 1 , wherein the cross section of the optical beam assumes an elliptical form before passing through said optical beam demagnifying and shaping device, and wherein said optical beam demagnifying and shaping device demagnifies and shapes the cross section of the optical beam along its major axis.
3 . The scanning type projector according to claim 1 , wherein said optical beam demagnifying and shaping device is configured including at least one trapezoidal or wedge-shaped prism, and wherein an incident angle for the optical beam at an incident surface of said optical beam demagnifying and shaping device is smaller than an outgoing angle for the optical beam at an outgoing surface.
4 . The scanning type projector according to claim 1 , wherein said at least one light source is two or more laser light sources emitting two or more optical beams having different wavelengths,
said beam demagnifying and shaping prism has a wavelength-selective reflective film on the outgoing surface of the prism, the reflective film having a function of transmitting a first optical beam having a given wavelength at a given transmittance and reflecting a second optical beam having a wavelength different from the wavelength of the first optical beam at a given reflectance,
said first optical beam is made to enter from a side of the incident surface of the beam demagnifying and shaping prism,
said second optical beam is made to enter from a side of the outgoing surface of the beam demagnifying and shaping prism, and
said first optical beam transmitted through the beam demagnifying and shaping prism and the second optical beam reflected off the beam demagnifying and shaping prism travel in the same optical path.
5 . The scanning type projector according to claim 1 , wherein said beam demagnifying and shaping prism is configured including at least one anamorphic lens having a first cross section of a given curvature and a second cross section of a different curvature perpendicular to the first cross section,
said optical beam assumes the form of collimated light and enters the beam demagnifying and shaping anamorphic lens, and
said beam demagnifying and shaping anamorphic lens permits the optical beam to pass while the collimated light is maintained.
6 . The scanning type projector according to claim 1 , wherein said beam demagnifying and shaping anamorphic lens has a cylindrical lenticular incident surface and a cylindrical lenticular outgoing surface,
a convex incident surface having a given radius of curvature and a concave outgoing surface having a given radius of curvature are formed in a first given direction of the cross section of said beam demagnifying and shaping anamorphic lens, and
a flat plate having perpendicular incident and outgoing surfaces is formed in a second given direction perpendicular to the first given direction.
7 . The scanning type projector according to claim 1 , wherein said collimator lens has a given cross section exhibiting a magnification and a cross section perpendicular to the given cross section exhibiting a different magnification.