Fresnel lens and projection display device using one such lens

A projection display device comprising:

• means of generating an image;
• means of projecting the image onto a screen;
• the screen comprising a Fresnel lens having a symmetry of revolution about a main axis,
• said Fresnel lens including at least one first area comprising first prisms, each first prism having a first side and a second side which forms with the main axis, an angle greater than that formed by the first side and the main axis,
• the second side of the first prism being designed to collimate, in line with the main axis;
• an incident ray from said projection means,
• wherein said Fresnel lens includes one second area comprising second prisms, each second prism having a first side and a second side which forms with a main axis an angle greater than that formed by the first side and the main axis,
• the second side of the second prism being designed to transmit, in a first direction different from the main axis, an incident ray from said projection means
• wherein, in at least one of said first and second areas, the first and second prisms work in a reflective mode, the first side of each of the first and second prisms refracting incident ray from said projection means to the second side of the corresponding which reflects the refracted ray to the output of said Fresnel lens, and
• wherein said Fresnel lens comprises at least one third area comprising third prisms, each third prism having a first side and a second side which forms with a main axis an angle greater than that formed by the first side and the main axis, and being designed to transmit an incident ray from said projection means in line with said main axis, the third prisms working in a reflective or transmissive mode different from the working mode of the first prisms.