Image combiner and image display device
An image combiner causes light from an image display element to be superimposed on light that is transmitted through a plate-form part positioned in front of the eye of a user. The light from the image display element reaches the eye of the user after being diffracted and reflected by a reflective type HOE inside the plate-form part. The HOE has a third-order or higher phase conversion action that depends on the position on the hologram plane. The distance Rd (calculated in air) between the light source that is on the side of the eyes of the observer during end-use (of the two light sources used to expose the HOE during the manufacture of the HOE) and the HOE is substantially greater than the distance Pd (calculated in air) between the exit pupil of the image combiner and the HOE.
1. An image combiner which comprises a reflective type holographic optical element, and which superimposes light from an image display unit on light passing through a main body of the image combiner, wherein:
the reflective type holographic optical element has a third-order or higher phase conversion action that depends on a position on a hologram plane, and
a distance Rd is substantially greater than a distance Pd,
where Rd is a distance calculated in air between (i) a light source located on a side of eyes of an observer during end-use of two light sources that are used to expose the reflective type holographic optical element during manufacture thereof and (ii) the hologram plane of the reflective type holographic optical element, and
where Pd is a distance calculated in air between an exit pupil of the image combiner and the hologram plane of the reflective type holographic optical element.
2. The image combiner according to claim 1 , wherein the distance Rd is at least twice the distance Pd.
3. The image combiner according to claim 2 , wherein the distance Rd is at least 100 mm.
4. An image display device comprising:
the image combiner according to claim 3 ; and
the image display, unit;
wherein at least a portion of the image display device containing the image combiner is mounted on the observer during use.
5. An image display device comprising:
the image combiner according to claim 2 ; and
the image display, unit;
wherein at least a portion of the image display device containing the image combiner is mounted on the observer during use.
6. The image combiner according to claim 1 , wherein the distance Rd is at least 100 mm.
7. An image display device comprising:
the image combiner according to claim 6 ; and
the image display, unit;
wherein at least a portion of the image display device containing the image combiner is mounted on the observer during use.
8. An image display device comprising:
the image combiner according to claim 1 ; and
the image display, unit;
wherein at least a portion of the image display device containing the image combiner is mounted on the observer during use.
9. An image display device comprising:
an image display unit; and
a light conducting part, which includes a reflective type holographic optical element, and which conducts light from the image display unit to eyes of a user;
wherein:
the reflective type holographic optical element has a third-order or higher phase conversion action that depends on a position on a hologram plane, and
a distance Rd is substantially greater than a distance Pd,
where Rd is a distance calculated in air between (i) a light source located on a side of eyes of an observer during end-use of two light sources that are used to expose the reflective type holographic optical element during manufacture thereof and (ii) the hologram plane of the reflective type holographic optical element, and
where Pd is a distance calculated in air between an exit pupil of the image combiner and the hologram plane of the reflective type holographic optical element.
10. The image display device according to claim 9 , wherein the distance Rd is at least twice the distance Pd.
11. The image display device according to claim 10 , wherein the distance Rd is at least 100 mm.
12. The image display device according to claim 9 , wherein the distance Rd is at least 100 mm.