Monday, February 04, 2013

Panasonic Develops Micro Color Splitters

Panasonic announces that it has found the holy grail of color image sensors design - the way to implement the color separation with no losses. Conventional sensors use a Bayer CFA that block 50-70% of the incoming light before it even reaches the sensor. Panasonic has developed unique "micro color splitters" that control the diffraction of light at a microscopic level directing each color to a respective pixel and that way achieved approximately double the color sensitivity in comparison with conventional sensors that use color filters:

Location of R-deflectors and detectors in the two-deflector method.
R-deflectors split colour to form the colours W + R in areas
between neighbouring R-deflectors, and W − R just beneath
the R-deflectors

This development is described in general terms in the Advance Online Publication version of Nature Photonics issued on February 3, 2013.

The developed technology has the following features:
  1. Using color alignment, which can use light more efficiently, instead of color filters, vivid color photographs can be taken at half the light levels needed by conventional sensors.
  2. Micro color splitters can simply replace the color filters in conventional image sensors, and are not dependent on the type of image sensor (CCD or CMOS) underneath.
  3. Micro color splitters can be fabricated using inorganic materials and existing semiconductor fabrication processes.
This development is based on the following new technology.
  1. A unique method of analysis and design based on wave optics that permits fast and precise computation of wave-optics phenomena.
  2. Device optimization technologies for creating micro color splitters that control the phase of the light passing through a transparent and highly-refractive plate-like structure to separate colors at a microscopic scale using diffraction.
  3. Layout technologies and unique algorithms that allow highly sensitive and precise color reproduction by combining the light that falls on detectors separated by the micro color splitters and processing the detected signals.
Panasonic holds 21 Japanese patents and 16 overseas patents, including pending applications, for this development.

Device optimization technologies leading to the creation of micro color splitters that control the phase of the light passing through a transparent and highly-refractive plate-like structure and use diffraction to separate colors on a microscopic scale:

Color separation of light in micro color splitters is caused by a difference in refractive index between a) the plate-like high refractive material that is thinner than the wavelength of the light and b) the surrounding material. Controlling the phase of traveling light by optimizing the shape parameters causes diffraction phenomena that are seen only on a microscopic scale and which cause color separation. Micro color splitters are fabricated using a conventional semiconductor manufacturing process. Fine-tuning their shapes causes the efficient separation of certain colors and their complementary colors, or the splitting of white light into blue, green, and red like a prism, with almost no loss of light.

Layout technologies and unique algorithms that enable highly sensitive and precise color reproduction by overlapping diffracted light on detectors separated by micro color splitters and processing the detected signals:

Since light separated by micro color splitters falls on the detectors in an overlapping manner, a new pixel layout and design algorithm are needed. The layout scheme is combined and optimized using an arithmetic processing technique designed specifically for mixed color signals. The result is highly sensitive and precise color reproduction. For example, if the structure separates light into a certain color and its complementary color, color pixels of white + red, white - red, white + blue, and white - blue are obtained and, using the arithmetic processing technique, are translated into normal color images without any loss of resolution.


  1. Holy grail for microoptics indeed!
    I had an optics Ph.D. working on this for several months at JPL in the early 1990's and he concluded that the angle of incidence problem made this difficult to achieve, and I believed him. So if Panasonic has solved this, it is interesting and maybe quite important.

  2. Holy grail indeed!

    In a sense, this is similar in sensitivity performance to the Foveon detection scheme where all the photons of every pixel were collected in 3 separate vertical layers.

    The Achilles heel of the Foveon approach was the poor color separation...

    It appears that the Panasonic approach may suffer from a similar color crosstalk issue... if they can significantly improve this color bleed, they will have a winner indeed!

  3. It would be good to see some angular response data indeed as EF suggests, was also my first concern when I saw this.

    Do note how they consider a microlens -- CFA -- microlens stack as "conventional"

    1. The last figure in the post gives some data on angular response. It's also discussed in the appendix on the Nature Photonics paper, available for free download on the link in the post.

  4. I believe you're right, at lower light levels saturation and colour accuracy will be like foveon as the deflected part forms too small a part of the signal to sucessfully extract the white component. Also would this have a maximum/minimum pixel size?


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