Kowa has filed a patent for a multifocal diffractive lens that efficiently uses light. The lens has a diffraction grating and produces multiple focal points for near and far vision. The focal position for far vision in polychromatic performance evaluation is closer to the lens than in monochromatic performance evaluation. The lens has three or more focal points and a combined shape of kinoform profiles. GlobalData’s report on Kowa gives a 360-degree view of the company including its patenting strategy. Buy the report here.
According to GlobalData’s company profile on Kowa, Eye-tracking wearables was a key innovation area identified from patents. Kowa's grant share as of September 2023 was 31%. Grant share is based on the ratio of number of grants to total number of patents.
Multifocal diffractive lens with efficient light usage
A recently filed patent (Publication Number: US20230301775A1) describes a multifocal diffractive lens with several unique features. The lens includes a diffraction grating that produces different focal points for different orders of light. Negative-order light creates a focal point for far vision, while 0-order light produces a focal point closer to the lens. Positive-order light produces a focal point even closer to the lens than the 0-order light. The lens has three or more focal points, and the diffraction grating is in a combined shape of kinoform profiles.
The patent also mentions the addition of correction terms to the kinoform profiles. These correction terms can account for factors such as the refractive index of the lens material and the pupil dilation ratio.
The multifocal diffractive lens can be either a trifocal or a quadrifocal lens. In the case of a trifocal lens, it has one additional focal point compared to a bifocal lens, and the near addition power is twice that of the bifocal lens. The number of diffraction fringes is the same between the two types of lenses. Similarly, a quadrifocal lens has two additional focal points compared to a bifocal lens, with a near addition power three times that of the bifocal lens. Again, the number of diffraction fringes remains the same.
The diffraction grating can have different shapes and configurations. It can be a combined shape of two kinoform profiles, with different heights or a constant height. The grating can also have a jagged part comprising planarized regions.
The multifocal diffractive lens is formed of optical material with normal dispersion and a refractive index between 1.45 and 1.56 at a wavelength of 546 nm. The lens has a pair of optical surfaces, with one surface including the diffraction grating and the other surface in a toric shape.
Overall, this patent describes a multifocal diffractive lens with various features and configurations that allow for improved vision correction and adaptation to different visual needs.