Projection optical system and image display device with refractive optical system to form an image on a receiving surface

1. A projection optical system that projects an image, the projection optical system comprising: a refractive optical system and a refractive/reflective optical element arranged in sequence from an image display surface toward a projection receiving surface, wherein the refractive optical system includes a plurality of lenses, wherein the refractive/reflective optical element includes an optical element unit that includes a reflection surface member including a reflection surface, and a refractive medium portion that is in tight contact with the reflection surface, the refractive medium portion includes an incidence surface and an emergence surface, and the reflection surface is a curved surface having refractive power, wherein an image-forming light beam emerging from the refractive optical system is caused to enter the refractive/reflective optical element from the incidence surface of the refractive medium portion, reflected by the reflection surface, caused to emerge from the emergence surface of the refractive medium portion, and formed into an image on the projection receiving surface as a projection image, wherein one or more intermediate images of the image displayed on the image display surface are formed between the refractive optical system and the emergence surface of the refractive/reflective optical element, and wherein one or two of the one or more intermediate images are in the refractive medium portion of the refractive/reflective optical element.

2. The projection optical system according to claim 1 ,

wherein at least one of the incidence surface and the emergence surface of the refractive medium portion has refractive power.

3. The projection optical system according to claim 2 ,

wherein the incidence surface and the emergence surface have refractive power.

4. The projection optical system according to claim 3 ,

wherein the incidence surface, the emergence surface, and the reflection surface have positive refractive power.

5. The projection optical system according to claim 1 ,

wherein the incidence surface and the emergence surface of the refractive/reflective optical element are formed from an identical surface.

6. The projection optical system according to claim 5 ,

wherein the incidence surface and the emergence surface identical to the incidence surface form a convex spherical surface, and the reflection surface is an aspherical surface rotationally symmetric with respect to an optical axis.

7. The projection optical system according to claim 1 ,

wherein the reflection surface member of the refractive/reflective optical element includes a radiating part on a surface opposite to the reflection surface.

8. An image display device, comprising:

an image display element; and

a projection optical system that projects an image displayed on an image display surface of the image display element in an enlarged manner on a projection receiving surface as a projection image,

wherein the projection optical system corresponds to the projection optical system according to claim 1 .

9. The image display device according to claim 8 ,

wherein the image display surface deviates from an optical axis toward a direction orthogonal to the optical axis, and forms an oblique light beam serving as the image-forming light beam.