Optical beam scanning device and image display device using the same
In a scanning image display device including a function to project and display a two-dimensional image on a projection screen using a deflecting unit that repeatedly operates a predetermined reflecting mirror surface to two-dimensionally scan a light beam, a large image distortion inevitably occurs, which is caused by the reflecting mirror surface that repeatedly and two-dimensionally operates for deflection. In order to solve the problem, a free-form surface lens or a wedge or trapezoid prism with a predetermined refractive index and a predetermined vertical angle is disposed in an optical path between the deflecting unit and the projection screen, thereby excellently correcting image distortion that occurs when scanning a light beam.
1. An optical beam scanning device comprising:
a light source; and
a deflecting mirror device which includes a predetermined optical reflection surface to operate for repeated deflection in two directions nearly orthogonal to each other, the deflecting mirror device having a function to deflect and scan a light beam emitted from the light source and reflected at the optical reflection surface in a first scanning direction and a second scanning direction nearly orthogonal to the first scanning direction,
wherein a wedge optical prism or a trapezoid optical prism with a predetermined vertical angle made of transparent optical glass or optical component plastic with a predetermined refractive index is disposed in an optical path of the light beam reflected at the optical reflection surface.
2. The optical beam scanning device according to claim 1 ,
wherein the vertical angle of the wedge optical prism or the trapezoid optical prism ranges from angles of 14° plus or minus 3°.
3. An optical beam scanning device comprising:
a light source; and
a deflecting mirror device which includes a predetermined optical reflection surface to operate for repeated deflection in two directions nearly orthogonal to each other, the deflecting mirror device having a function to deflect and scan a light beam emitted from the light source and reflected at the optical reflection surface in a first scanning direction and a second scanning direction nearly orthogonal to the first scanning direction,
wherein a compound prism is disposed in an optical path of the light beam reflected at the optical reflection surface, the compound prism being formed of a wedge or trapezoid first optical prism with a predetermined vertical angle made of transparent optical glass or optical component plastic with a predetermined refractive index and a predetermined Abbe number and a second optical prism with a predetermined vertical angle made of optical glass or optical component plastic with a predetermined Abbe number different from at least the Abbe number of the first optical prism, the first optical prism being bonded to the second optical prism.
4. An optical beam scanning device, wherein:
the wedge optical prism, the trapezoid optical prism, or the compound prism according to claim 1 is disposed at a light beam emission opening of the beam scanning device or an image display device using the beam scanning device; and
the prism also serves as a dustproof transparent window member by sealing the opening with the prism.
5. An optical beam scanning device comprising:
a light source; and
a deflecting mirror device which includes a predetermined optical reflection surface to operate for repeated deflection in two directions nearly orthogonal to each other, the deflecting mirror device having a function to deflect and scan a light beam emitted from the light source and reflected at the optical reflection surface in a first scanning direction and a second scanning direction nearly orthogonal to the first scanning direction,
wherein a compound prism is disposed at a position at which a going light beam and a returning light beam enter from in nearly reverse directions from each other, the going light beam being emitted from the light source and entering the optical reflection surface, the returning light beam being reflected at the optical reflection surface, the compound prism being formed of a wedge or trapezoid first optical prism with a predetermined vertical angle made of transparent optical glass or optical component plastic with a predetermined refractive index and a predetermined Abbe number and a second optical prism with a predetermined vertical angle made of optical glass or optical component plastic with a predetermined Abbe number different from at least the Abbe number of the first optical prism, the first optical prism being bonded to the second optical prism.
6. An optical beam scanning device comprising:
a light source; and
a deflecting mirror device which includes a predetermined optical reflection surface to operate for repeated deflection in two directions nearly orthogonal to each other, the deflecting mirror device having a function to deflect and scan a light beam emitted from the light source and reflected at the optical reflection surface in a first scanning direction and a second scanning direction nearly orthogonal to the first scanning direction;
wherein a wedge or trapezoid first optical prism with a predetermined vertical angle made of transparent optical glass or optical component plastic with a predetermined refractive index and a predetermined Abbe number and a second optical prism with a predetermined vertical angle made of optical glass or optical component plastic with a predetermined Abbe number different from at least the Abbe number of the first optical prism are disposed at positions apart from a predetermined distance;
wherein a going light beam emitted from the light source is transmitted through at least one of the first optical prism and the second optical prism, and then enters the optical reflection surface; and
wherein a returning light beam reflected at the optical reflection surface is in turn transmitted through the first and second optical prisms.
7. An image display device comprising:
the optical beam scanning device according to claim 1 .
8. The optical beam scanning device according to claim 6 , wherein the vertical angle of the first optical prism ranges between angles of 25° to 30°.