Panasonic Develops Technology for Highly Sensitive Image Sensors

Panasonic Develops Technology for Highly Sensitive Image Sensors Using Micro
Color Splitters 
Osaka, Feb 4, 2013 - (JCN Newswire) -  Panasonic Corporation has developed
unique "micro color splitters", which separate the light that falls
on image sensors by exploiting light's wavelike properties. Applying them
to actual image sensors allows bright color images to be achieved even under
low-light conditions. This development makes color filters unnecessary by using
the micro color splitters that control the diffraction(1) of light at a
microscopic level. Panasonic has achieved approximately double the color
sensitivity in comparison with conventional sensors that use color filters. 
Image sensors are used in devices like smartphones, digital still cameras and
video cameras, as well in security, vehicle parking, office, and healthcare
applications - anywhere, in fact, that digital imaging is needed. Conventional
color image sensors use a Bayer array(2), in which a red, green, or blue
light-transmitting filter is placed above each sensor. These filters block 50 -
70% of the incoming light before it even reaches the sensor. Progress is being
made in increasing the resolution of image sensors used in mobile and other
devices by reducing pixel size, but demand for higher-sensitivity cameras is
also increasing. Panasonic has developed a new technology that can be applied
to existing or future sensors to enable them to capture uniquely vivid color
images. 
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(3) or
CMOS(4)) 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. 
This development is described in general terms in the Advance Online
Publication version of Nature Photonics issued on February 3, 2013. 
More on the Technology 
1. Unique method of analysis and design based on wave optics permitting fast
and precise computation of wave-optics phenomena 
FDTD5 is widely used to analyze light in wave form, but its heavy computation
workload has up to now made it impractical for designing micro color splitters.
On the other hand, BPM(6) is an effective method of fast computation, but it
has lower precision than FDTD and cannot accurately simulate color splitting.
This prompted Panasonic to develop a practical and original design method that
permits fast and precise computation of wave-optics phenomena. This technology
allows the precise modeling of optical phenomena such as reflection,
refraction, and diffraction by modeling spaces in regions with different
optical constants and applying BPM to the spaces.  This method can be applied
not only to the design of micro color splitters, but can be extended to the
design of other nano-scale optical processing systems. 
2. 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. 
3. 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) Diffraction: Behavior of light as a wave on the wavelength (nanometer)
scale. Various phenomena occur when a wave encounters an obstacle.
(2) Bayer array: The arrangement of color filters used in most single-chip
digital imaging sensors used in digital cameras, camcorders, and scanners to
create a color image. The filter pattern is 50% green, 25% red and 25% blue.
(3) Charge Coupled Device Image Sensor (CCD sensor): A type of solid-state
image sensing device for digital imaging, used in digital video cameras of all
types. It has higher sensitivity and lower noise than other sensing devices.
(4) Complementary Metal Oxide Semiconductor Image Sensor (CMOS sensor): A
solid-state image sensing device for digital imaging using CMOS.
(5) Finite-Difference Time-Domain method (FDTD): FDTD is a versatile modeling
technique used to solve Maxwell's equations by spatial and temporal
discretization.
(6) Beam Propagation Method (BPM): A numerical analysis technique in
electromagnetics for solving the Helmholtz equation under conditions of a
time-harmonic wave. 
About Panasonic 
Panasonic Corporation is a worldwide leader in the development and manufacture
of electronic products in three business fields, consumer, components &
devices, and solutions. Based in Osaka, Japan, the company recorded
consolidated net sales of 7.85 trillion yen for the year ended March 31, 2012.
Panasonic's stock is listed on the Tokyo, Osaka, Nagoya and New York
(NYSE:PC) Stock Exchanges. The company has the vision of becoming the No. 1
Green Innovation Company in the Electronics Industry by the 100th year of its
founding in 2018. For more information on Panasonic, its brand and commitment
to sustainability, visit the company's website at http://panasonic.net/. 
Contact: 
Tokyo Public Relations Office
Panasonic Corporation
Tel: +81-3-3574-5664
Fax: +81-3-3574-5699 
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