Projection optical system having a wedge prism

A projection optical system includes a light source emitting light, a light valve with a surface in front of the light source, and a wedge prism disposed in the optical path from the light source to the light valve. By means of the wedge prism with different sectional thickness, the optical path and focus position of the light beam can be corrected. Therefore, the distortion produced by oblique incidence on to the light valve can be improved such that the light optical focus on the surface of the light valve to achieve the improvement of light spot on light valve and raise the uniformity, collection efficiency, and brightness.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a projection optical system, and more particularly to a projection optical system having a wedge prism for light collection efficiency.

2. Description of the Related Art

As shown inFIG. 1, a light source module1, a color wheel3, an integration rod4, and a relay lens5are coaxial in a prior art non-telecentric projection optical system, but a light valve6and a projection lens7aren't coaxial with the above-mentioned devices. As the light source module1producing a illuminating light beam, travels through the color wheel3, the integration rod4, and the relay lens5into a reflection mirror8. The reflection mirror8reflects the light beam obliquely into the light valve6. After dealt by the light valve6, the images through the projection lens are finally formed on the projection screen9.

Because of the reflection illuminating light beam's oblique incidence on the light valve6, the reflection optical paths from the reflection mirror8to each pixel on the light valve6do not extend over the same distance. As shown inFIG. 2, the reflection illuminating light beam should have the same optical path and focus on focuses Fa, Fb, and Fc, but because of the different optical path lengths, only the central focus Fb can focus on the right position. The focuses fa and Fc can't certainly focus and cause the defocus phenomenon. As a result, the illuminating light beam can't certainly focus on the light valve6and cause the illuminating area on the plane of the light valve6to increase. As shown inFIG. 3, the light spot (shown in A, B) on the same plane of the light valve6is deformed, and forms lower and non-uniform brightness, affecting the collection efficiency of the light valve6.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a projection optical system having a wedge prism, which raises the uniformity, collection efficiency, and brightness of the light valve.

Another object of the present invention is to provide a projection optical system having a wedge prism, which improves the defocus phenomenon produced by oblique incidence on to the light valve.

Another object of the present invention is to provide a prism optical system having a wedge prism, which disposes the wedge prism in the optical path to correct the illuminating light beam focus position and the distortion of the light spot on the light valve surface.

To achieve the above and other objects, in the present invention, a projection optical system having a wedge prism includes a light source emitting light, a light valve with a surface in front of the light source, and a wedge prism disposed in the optical path from the light source to the light valve. By means of the wedge prism with different sectional thickness, the optical path and focus position of the light can be corrected. Therefore, the distortion produced by oblique incidence on to the light valve can be improved such that the light optical focus on the surface of the light valve to achieve the improvement of light spot on light valve and raise the uniformity, collection efficiency, and brightness.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 4which shows the first embodiment of the present invention, a projection optical system having a wedge prism15sequentially comprises a light source10, a color wheel12, an integration rod13, a relay lens14, a wedge prism15, a reflection mirror16, a light valve17having a surface171, a projection lens18, and a projection screen19, wherein a surface171, a projection lens18, and a projection screen19are not coaxial with the other above-mentioned devices.

An illuminating light beam bundle101is produced by the light source10, and travels through the color wheel12, the integration rod13, and the relay lens14to filter, make uniform, and collect the light beam. The relay lens14directs an illuminating light beam bundle into the wedge prism15. The wedge prism15includes two opposite surfaces151and152, and has different sectional thicknesses. The illuminating light beam102bundle is incident on the surface151of the wedge prism15, and then refracted, and passes through the surface152onto the adjacent reflection mirror16. The reflected illuminating light beam103passes through the wedge prism15again, is refracted by the wedge prism15, passes through the surface151, and is obliquely incident on the light valve17. After reflection by the light valve17, the illuminating light beam103passes through the projection lens18and finally projects onto the projection screen19.

Referring toFIG. 5, an optical system of the prior art only uses a reflection mirror16to reflect an optical path as shown by the dotted line. As known, the illuminating light beam102from the relay lens14is directly incident on the reflection mirror16, and a reflection illuminating light beam104focuses on the focus Fg, focus Fh, and focus Fi. However, the focuses Fg and Fi aren't on the light valve17. The present invention allows the optical path to be adjusted by the wedge prism15as the real line. The illuminating light beam102from the relay10passes through the wedge prism15into the reflection mirror16and then the reflected illuminating light beam10passes through the wedge prism15into the light valve17. By adjusting the thickness of the prism15to re-focus the reflected illuminating light beam103on the focuses Fg′, Fh′, an Fi′, the focuses Fg′, Fh′, and Fi′ are in the same line and parallel to the light valve17. By horizontally shifting the light valve17to the plane of the focuses Fg′, Fh′, a Fi′, the light valve17shifts to the light valve17A to focus the illuminating light beam and form a uniform light spot, which modifies the blurry and deformed light spot of the prior art and lowers the lightness loss caused by the defocus. The total lightness of the light valve is higher than the prior art to raise brightness and efficiency.

By adding the wedge prism15, the illuminating light beam passes through the different thicknesses of the prism15. The different thicknesses depend on the distance of the light path to the light valve17. By means of different refraction rates and thicknesses of the wedge prism, the optical path and focus position of the light can be corrected. Furthermore, horizontally shifting the position of the light valve17to focus the illuminating light beam on the light valve17resolves the defocus problem and raises uniformity, collection efficiency, and the brightness of the light valve17.

Referring toFIG. 6which shows a second embodiment of the present invention, an optical system of the present embodiment basically has the same construction with the above-mentioned first embodiment. The equal or similar devices are marked by the same reference numerals. The difference between the present embodiment and the first embodiment is to combine the wedge prism15surface152of the first embodiment with the adjacent reflection mirror16and form the surface152with a reflection surface such as cladding material or a total internal reflection surface. By means of the wedge prism15with different thicknesses to revise focus position, the light beam from the relay lens14is reflected and focused right on the light valve17to improve the defocus that causes the brightness loss from the edges of the light valve17.

The present invention is not limited in using the wedge prism to resolve the distortion produced by oblique incidence, but for any optical devices that the light beam impinges into the optical devices by oblique incidence to dispose the wedge prism in the optical path into which the illuminating light beam impinges to correct the focus position onto the optical devices so as to achieve the improvement of the light spot uniformity, collection efficiency, and brightness.

It will be apparent to those skilled in the art that in light of the forgoing disclosure, many alternations and modifications are possible in the practice of this invention without departing from the spirit or scoop thereof. Accordingly, the scoop of the invention is to be considered in accordance with the substance defined in the following claims.