Display device having a holding device that can be placed on the head of a user
A display device includes a holding device that can be placed on the head of a user. An image-generating module and an imaging lens system can be secured on the holding device. The latter includes a spectacle lens with a curved front and a curved back. It projects the image generated when the holding device is placed on the head such that the user can perceive it superimposed on the surroundings. Light from the image-generating module is coupled into an optical channel in the spectacle lens. It is conducted in the optical channel to an exit section and coupled via the exit section out of the spectacle lens. The optical channel includes in the region of the front and back a Fresnel structure with a plurality of facets on which the light conducted in the optical channel is reflected, and which are aligned parallel to one another.
1. A display device, comprising:
a holding device configured to be placed on the head of a user;
an image-generating module, secured on the holding device, configured to generate an image; and
an imaging lens system, secured on the holding device, which includes a spectacle lens with a curved front and a curved back, and which is configured to project the image generated when the holding device is placed on the head such that the user can perceive it superimposed on the surroundings,
wherein the light coming from the image-generating module is coupled via an entrance section into an optical channel in the spectacle lens, conducted in the optical channel to an exit section and coupled via the exit section out of the spectacle lens,
wherein the optical channel includes, in a region of the curved front and the curved back, in each case, a first and a second Fresnel structure with a first facet and a second facet, on which the light conducted in the optical channel is reflected, and which are aligned parallel to one another,
wherein owing to the first and second facets, the optical channel acts optically as a plane-parallel plate, and
wherein the first facets are formed on the back of the spectacle lens and the second facets are formed on the front of the spectacle lens.
2. The display device according to claim 1 , wherein the entrance section includes, on the front of the spectacle lens, a third Fresnel structure with third facets, which are aligned parallel to one another and are tilted relative to the first and second facets.
3. The display device according to claim 2 , wherein the third Fresnel structure only brings about a bending of the beam path and does not have an imaging property.
4. The display device according to claim 2 , wherein the third Fresnel structure brings about a bending of the beam path and at the same time has an imaging property.
5. The display device according to claim 1 , wherein the exit section on the front of the spectacle lens includes a third Fresnel structure with third facets, which are aligned parallel to one another and are tilted relative to the first and second facets.
6. The display device according to claim 5 , wherein the third Fresnel structure only brings about a bending of the beam path and does not have an imaging property.
7. The display device according to claim 5 , wherein the third facets form a continuous saw-tooth structure.
8. The display device according to claim 5 , wherein the third facets are arranged at a distance from one another.
9. The display device according to claim 5 , wherein the third facets are coated with a partially reflecting layer.
10. The display device according to claim 1 , wherein the light is conducted in the optical channel by total internal reflection.
11. The display device according to claim 1 , wherein the image-generating module includes an image transmitter and a collimating lens system arranged after the image transmitter.
12. The display device according to claim 1 , wherein the first and second facets of the first and second Fresnel structures virtually cancel out the effect of the curved front and the curved back of the spectacle lens.