Substrate-guided wave-based transparent holographic center high mounted stop light and method of fabrication thereof
Multiple pairs of substrate-guided wave-based holograms (SGWHs) are laminated to a common thin substrate to form a transparent substrate-guided wave-based holographic CHMSL (SGWHC) that diffracts playback LED illumination over a wide angular range. This device is made pursuant to a technique that includes the steps of recording a first set of SGWHs with one setup, that upon playback, will couple and guide the diffracted light inside the substrate, and a second set of SGWHs recorded with another setup, that will diffract and couple the guided light out.
1. A light assembly for a vehicle comprising a substrate guided wave based transparent hologram (SGWH) having:
a) a first light source transmitting a first light beam in a first direction through a beam expander to illuminate a first substrate guided wave based hologram;
b) a second light source different from the first light source transmitting a second light beam different from the first light beam and in a second direction different from the first direction through a beam expander to illuminate a holographic recording thin film;
c) said first light beam diffracted on the first substrate guided wave based hologram and propagating along a substrate by internal reflection;
d) said holographic recording thin film secured to the substrate whereby the second light beam passes through a crossed lenticular lens and then an elliptical light shaping diffuser to homogenize the second light beams, and then couples with the first diffracted light beam within the substrate and records the second hologram;
e) wherein the coupled first and second light beams retrieved by the second hologram outputs an image or illuminates an area outside the substrate when said first hologram is illuminated with the light source.
2. The light assembly of claim 1 , wherein the substrate is a transparent material with the index of refraction close to the hologram index of refraction.
3. The light of assembly of claim 1 , wherein the substrate is a material selected from the group of acrylic, glass and polycarbonate.
4. The light assembly of claim 1 , wherein the first light source is an LED.
5. The light assembly of claim 1 wherein the second beam passes through a second thin film after said lenticular lenses and diffuser.
6. The light assembly of claim 1 wherein the first and second thin film comprises a polyester or polycarbonate film with holographic polymer.
7. The light assembly of claim 1 wherein the polyester film is a polyethylene naphthalate film.