Tuesday, July 05, 2011

Samsung Applies for Transparent Pixel Patent

Samsung patent application US20110156114 has quite an entertaining title "Image sensor using light-sensitive transparent oxide semiconductor material". The patent summary says "Example embodiments include an image sensor that may reduce the size of a unit pixel by using a light-sensitive transparent oxide semiconductor material as a light-sensing layer." The base structure consists of interleaved transparent sensing layers 110, 120 and 130 and color filter layers 140 and 150, separated by insulating layers 115:

"Light incident on the image sensor 100 constructed as described above may be detected by the first through third light-sensing layers 110, 120, and 130 with respect to color components of the light. For example, the first light-sensing layer 110 may detect all of red, green, and blue light. Part of the light incident on the image sensor 100 travels toward the second light-sensing layer 120. For example, the first filter layer 140 may block only light having blue wavelengths and transmit light having wavelengths other than the blue wavelengths. Accordingly, the second light-sensing layer 120 may detect mostly red and green light. Part of the light passing through the second light-sensing layer 120 travels toward the third light-sensing layer 130. The second filter layer 150 may block only light having green wavelengths and transmit light having wavelengths other than the green wavelengths. Alternatively, the second filter layer 150 may transmit only light having red wavelengths and block light having wavelengths other than the red wavelengths. Accordingly, the third light-sensing layer 130 may detect mostly red light."


  1. It is a wonder that this past patent scrutiny -- since the semiconductor layers are "transparent", they absorb no photons; since they are "light sensitive" they detect the passing of photons. The only explanation would be a new mechanism with new physics. Sounds like perpetual motion.

  2. It is just a patent application. There has been no scrutiny yet. The English in the application is not perfect but it seems to me it is NOT nonsense. If the absorbing layers were a-Si, for example, and thin, they would be partially transparent. So, I think this would conceptually work but due to color overlap, YSNR would probably be lower than RGBW. On the other hand, the color resolution would be much higher and without aliasing.
    Low noise readout and lag is always the issue in these thin film schemes and that would probably further deteriorate YSNR.

    Meanwhile, if Invisage can make their device achieve high performance (so far not yet demonstrated)then there would be hope for this device.

  3. I think this is another application where the actual idea is weakened and obscured by patent language that tries for too much. The key element - a "light-sensitive oxide semiconductor layer" - does not seem to be defined precisely, at least not in the US PTO portion of the application. It is to be used "as a light-sensing layer" (claim 1), but "may include a plurality of light-sensing layers" (claim 2) which may be interspersed with filter layers (claim 3) and insulating layers (claim 4). These claims make the "light-sensitive oxide semiconductor layer" seem more like a set of layers, except the element is also recited as a more single-layer-like structure with "opposite sides" (claims 9 and 13).

    Et cetera.

    The core of the invention seems to be that one could make a color pixel with oxide layers for photon capture and filter and insulation layers between, all on top of a substrate. I think it would be pretty hard to prove novelty and non-obviousness for this. For one thing, the layer cross-section in Fig. 1 is substantially identical to the structure of analog color film used from the 1930s on. This in combination with the ability to make light-sensing and color-filtering surface layers on a semiconductor substrate immediately suggests the core idea to me. Also, it seems like the various "layers" recited in the claims are also present in Foveon pixels, albeit below the surface.


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