![]() Original Assignee Dai Nippon Printing Co Ltd Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.) ( en Inventor Satoshi Shioda Mikiko Hojo Hiroyuki Otaki Kenji Ueda Tetsuya Toshine Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) Expired - Lifetime Application number EP10010585.7A Other languages German ( de) Google Patents Relief hologram or diffraction grating sheet and forgery-preventing sheet comprising the sameĭownload PDF Info Publication number EP2309339B1 EP2309339B1 EP10010585.7A EP10010585A EP2309339B1 EP 2309339 B1 EP2309339 B1 EP 2309339B1 EP 10010585 A EP10010585 A EP 10010585A EP 2309339 B1 EP2309339 B1 EP 2309339B1 Authority EP European Patent Office Prior art keywords layer hologram modulus young diffraction grating Prior art date Legal status (The legal status is an assumption and is not a legal conclusion. Google Patents EP2309339B1 - Relief hologram or diffraction grating sheet and forgery-preventing sheet comprising the same Typically, the cost of producing a master diffraction grating is expensive and by supplying replica gratings (which offer almost indistinguishable performance), one master may produce thousands of replicas, lowering the unit cost of the diffraction grating.EP2309339B1 - Relief hologram or diffraction grating sheet and forgery-preventing sheet comprising the same A blazed grating has a ‘saw tooth’ profile and normally offers higher efficiency.Ī commercial diffraction grating is generally a replica grating produced from a sub-master, which may be a number of generations down from the master diffraction grating. A sinusoidal grating generally offers lower efficiency than a blazed grating, but often gives a broader spectral coverage. Transmission gratings are usually supplied with an antireflection coating.Ī diffraction grating can have a sinusoidal or blazed profile. Reflection gratings are normally coated with a reflective coating, usually aluminum with a protective overcoat for UV-VIS-NIR use or gold for IR use. ![]() The most common type of diffraction grating are plane gratings and concave gratings although they can also be other profiles such as convex or toroidal depending on the application. ![]() There are typically two different types of diffraction grating – the ruled grating and the holographic grating.Ī ruled diffraction grating is produced by a ruling engine that cuts grooves into the coating on the grating substrate (typically glass coated with a thin reflective layer) using a diamond tipped tool.Ī holographic diffraction grating is produced using interference lithography which results in a smooth groove surface and eliminates the periodic errors found in ruled gratings.Ī diffraction grating can be a reflection grating or a transmission grating. ![]() The groove density, depth and profile of a diffraction grating dictate the spectral range, efficiency, resolution and performance of the diffraction grating. A diffraction grating is an optical element that diffracts energy into its constituent wavelengths.
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