Abstract
Manufacturing methods are disclosed to produce a seamless hologram using a free-form-lens enabling arbitrary adjustment of diffraction angle and also a thick hologram made of transparent inorganic materials and heat and UV resistant is disclosed.
Claims
1. A see-through display comprising a display device and a projection lens system which projects the image of said display device a combiner which integrates a real image in front of a viewer and the projected image and a hologram on the combiner comprising a photopolymer wherein the photopolymer exposed for recording with two coherent beams and at least one of the beams is focused on the photopolymer with at least one free-form lens and the entire viewing surface of the photopolymer is exposed seamlessly by the free-form lens
2. The see-through display of claim-1 wherein the hologram is exposed with at least three colors.
3. The see-through display of claim-1 wherein one of recording beams is collimated.
4. The see-through display of claim-1 wherein the two recording beams are combined with a beam splitter,
5. A manufacturing method having the steps of: calculating a function which enables to know the diffraction angle of hologram to maximize the resolution of image of combiner of see-through display and calculating the tilt angle of micro stripe in the hologram and calculating the angles of two recording beams so that the middle angle between said two beams coincide with said tilt angle of micro stripe in the hologram and design at least one tree-form-lens so that the incident beams to the hologram coincide with said angles of two recording beams.
6. A see-through display comprising a display device and a projection lens system which projects the image of said display device and a combiner which integrates a real image in front of a viewer and the projected image and a hologram on the combiner wherein a hologram is made of transparent and inorganic material comprising a transparent substrate and at least two patterned layers of inorganic material whose refractive indices differ from that of said substrate and the patterned layers have a periodical structure and diffract incident light whose incident angle and wavelength and the pitch of the periodical structure meet Bragg's law.
7. The see-through display of claim-6 wherein the substrate is made of oxide and substantially transparent.
8. The see-through display of claim-6 wherein the patterned layers are made of nitride and substantially transparent.
9. The see-through display of claim-6 wherein the patterned layers are at least 2 microns thick.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 illustrates the processes to form a hologram by applying two coherent beams superimposed on a photopolymer wherein the distribution of the light intensity of two interfered beams creates periodic stripes in a certain direction and in a certain pitch. The refractive index or photopolymer varies depending on the intensity or more particularly proportional to the intensity. The varied refractive index be fixed permanently with a chemical process. This process is called as Recoding of hologram.
[0015] FIG. 2 illustrates how an incident beam that is diffracted by the recorded hologram structure and the incident beam enters the hologram wherein there are high refractive index areas and low refractive index areas and the beam will be reflected by the stripes as if the stripes are mirrors, if the angle and wavelength of the incident beam and the pitch of stripes meet so called Bragg's law. Unless otherwise, the incident light beam passes through.
[0016] FIG. 3 illustrates a conventional process, wherein a transmissive hologram with a mask pattern so that an image shows up (playback) when an illumination (marked B) light beam is provided.
[0017] FIG. 4 illustrates an example of recording a transmissive hologram using a step-by-step exposure, wherein 4004 and 4014 are Galvano mirrors to adjust the angle of incident beams. This system allows the adjustment of angle of incident beams arbitrarily, the landing location of beam varies with the mirror angle and requires an adjustment every exposure.
[0018] FIG. 5 illustrates an example of recording a reflective hologram using a step-by-step exposure, wherein 5031 and 5032 are Galvano mirrors to adjust the angle of incident beams. This system allows the adjustment of angle of incident beams arbitrarily, the landing location of beam varies with the mirror angle and requires an adjustment every exposure.
[0019] FIG. 6 is an example of recording a reflective type of hologram using F lenses (6002 and 6003), so that the system does not require any adjustment of exposure location, because regardless of the angles of Galvano mirrors (6005 and 6035), the location of exposure is fixed using F- lenses
[0020] FIG. 7 is an example of recording a reflective type of hologram using an elliptic mirror (7023), wherein the light starting from one of foci is always reflected toward the second focus, so that the system does not require any adjustment of exposure location, because regardless of the angles of Galvano mirrors (6005 and 6035), the location of exposure is fixed to the second focus.
[0021] FIG. 8 illustrates an example of recording, a transmissive hologram using step-by-step exposure. In case of transmissive recording, two recording light sources often interfere due to the narrow space between a lens and a hologram plate (5004).
[0022] FIG. 9 illustrates an example of to avoid the interference of tools, a beam splitter (9007) is used. For the beam splitter, half-mirror or a PBS (polarized beam splitter) can be used. Even overcoming these difficulties, there is residual non-uniformity of exposure remains.
[0023] FIG. 10 is a system to record a reflective type of hologram.
[0024] FIG. 11 is a system to record a transmissive type of hologram,
[0025] FIG. 12 is a system to record a transmissive type a hologram with a beam splitter.
[0026] FIG. 13 shows an example of conventional DOE (diffractive optical element).
[0027] FIG. 14 shows an example of thick hologram made of inorganic material,
DETAIL DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
[0028] FIG. 10 is an example of this invention to record a reflective type of hologram, wherein 1002 is a collimated light beam and a coherent light beam (1006) is lead to a free-form-lens (1005) and an aspherical lens (1004) so that the direction and the location of recording light beam (1003) is adjusted to meet the required diffraction angle at each location of hologram (1001). This system does not have non-uniformity due to stepping, because the entire area is exposed simultaneously without any division. This system provides completely arbitrary adjustment of diffraction angle
[0029] FIG. 11 is an example of this invention to record a transmissive type of hologram, wherein 1105 is a collimated light beam and a coherent light beam (1101) is lead to a free-form-lens (1102) and an aspherical lens (1103) so the direction and the location of recording light beam (1104) is adjusted to meet the required diffraction angle at each location of hologram (1107). This system does not have non-uniformity due to stepping, because the entire area is exposed simultaneously without any division. This system provides completely arbitrary adjustment of diffraction angle and seamless exposure.
[0030] FIG. 12 is an example of this invention to record a transmissive type of hologram when the spare between the lens system and hologram is not sufficient, wherein (1206) is a collimated light beam and is reflected by a beam splitter (1207) toward a hologram(1205) and a coherent light beam (1201) is lead to a free-form-lens (1202) and an aspherical lens (1203) so that the direction and the location of recording light beam (1204) is adjusted to meet the required diffraction angle at each location of hologram (120). This system does not have non-uniformity due to stepping, because the entire area is exposed simultaneously without any division. This system provides completely arbitrary adjustment of diffraction angle and seamless exposure.
[0031] FIG. 13 shows an example of DOE (diffractive optical element). On a substrate (1302), blazed structure (1301) is created either by machining or lithographical method as shown in (FIG. 13). A DOE made of inorganic material can be produced much more precisely and reliably than hologram made of organic photopolymer which deforms during recording and chemical processes. However due to its thin structure (often submicron), the performance is often limited compared with hologram which can be made thicker than DOE.
[0032] FIG. 14 shows an example of this invention of thick hologram made of inorganic material. Using lithography and deposition tools, thicker hologram can be made of inorganic material such as dielectric material including oxide and nitride. 140 is a transparent inorganic dielectric material stich as glass and 1402 is another transparent inorganic material with higher refractive index than that of 1401. With a multi-layer structure using lithography, deposition and etching, the tilt angle shown as 1406 and the pitch between stripes (1405) can be controlled precisely and arbitrarily.
[0033] The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, to thereby enable others skilled in the art to best utilize the disclosure and various embodiments with various modifications as ate suited to the particular use contemplated.
