Cameras used in outdoor scenes require high visibility performance under various environmental conditions. We present
a visibility improvement technique which can improve the visibility of images captured in bad weather such as fog and
haze, and also applicable to real-time processing in surveillance cameras and vehicle cameras. Our algorithm enhances
contrast pixel by pixel according to the brightness and sharpness of neighboring pixels. In order to reduce computational
costs, we preliminarily specify the adaptive functions which determine contrast gain from brightness and sharpness of
neighboring pixels. We optimize these functions using the sets of fog images and examine how well they can predict the
fog-degraded area using both qualitative and quantitative assessment. We demonstrate that our method can prevent
excessive correction to the area without fog to suppress noise amplification in sky or shadow region, while applying
powerful correction to the fog-degraded area. In comparison with other real-time oriented methods, our method can
reproduce clear-day visibility while preserving gradation in shadows and highlights and also preserving naturalness of
the original image. Our algorithm with low computational costs can be compactly implemented on hardware and thus
applicable to wide-range of video equipments for the purpose of visibility improvement in surveillance cameras, vehicle
cameras, and displays.
The authors have successfully developed a six-primary-color liquid crystal display using six-color LEDs. More specifically, a prototype of a six-primary-color liquid crystal display having a color gamut of 170% or wider then that of conventional techniques has been constructed. Furthermore, this monitor has a newly developed calibration system using an integrated color sensor, so that it can keep its white point chromaticity stable.
Authors have developed a wide color gamut and high brightness WUXGA LCD monitor with color calibrator. This monitor uses three color LED, including red, green and blue, as the light source for the backlighting. This framework involves a problem that the chromaticity points of white color (white balance) shifts over time due to the changes in the wavelength of emitted beams and emission luminance (efficiency) of the LEDs, which work as the light source, depending on the temperature． It also has a tendency to deteriorate in color non-uniformity performance to some extent because of the variation of luminance of individual LED elements and other factors compared to the backlighting of light source of conventional Cold Cathode Fluorescent light (CCFL). Authors have develop a color calibrator that has: 1) a feedback control circuit via optical sensors in which backlighting is incorporated, 2) a color non-uniformity control through modulation of image signals, and 3) a gamma-correction function, in order to solve this problem and to enable introduction of this device into applications that require strict color control.
This research was organized in part by the New Energy and Industrial Technology Development Organization, Japan (NEDO).
The authors have developed two types of wide color gamut monitor and compared their characteristics. This paper provides an introduction to the color reproduction and standard color space of displays as well as an interpretation of the two types of typical wide color gamut displays that are currently under development. The CRT displays with a wide color gamut are rich in gray levels and viewing angle characteristics while the LCD displays with a LED backlight style have high brightness performance and a broad color gamut. Both types of display support the color gamut of Adobe RGB, enabling compatibility with the extended color space, now beginning to be disseminated, and they also provide a breakthrough for industries that need color management.
We developed an LCD module that uses a color conversion circuit to improve imperfect color reproduction in the LCD panel. Our module implements a color conversion circuit that uses a matrix calculation we developed. This color conversion circuit supports motion picture display and real-time processing, enabling desired color conversion characteristics and facilitating use of 2 modes of color conversion characteristics by selection sRGB mode and consumer-TV-like color mode consumer-TV-like color mode. The international sRGB standard is the default RGB color space for multimedia, in which 'reference image display system characteristics' are specified, i.e., a display device must have characteristics close to sRGB characteristics to properly display color image data conforming to sRGB. This is why the sRGB specification for liquid crystal displays has been defined. Our TFT-LCD module achieves less than one tenth the color difference for the sRGB specification. Devices with low color reproducibility are improved using a color conversion circuit to increase apparent color depth, but conventional approaches to this have such adverse effects as color saturation in high-chroma areas and emphasized color noise in dark areas. Our module achieves consumer-TV-like color by implementing a new color conversion circuit that includes a gamut compression function to solve such problems.
As many color devices, such as color displays, color printers, digital cameras, are commonly used, it is well known that colors displayed on two color devices are different from each other. This difference in color necessitates the use of color matching techniques, especially gamut compression, to compress the colors displayed on the device having the larger gamut onto a device having a smaller color gamut. In this paper we introduce a modified method of gamut compression using correlate with modified perceptible difference. Previously we introduced a color difference in HVC color space and also sensitivity coefficients to improve the subjective quality of the gamut compression that is to compress out of gamut color to inside gamut color. That was to have determined the sensitivity coefficients for Hue, Value and Chroma in HVC color space based on the subjective evaluations between different color devices. Then we applied the sensitivity coefficients to gamut compression. Carrying out subjective experiment, the result showed that this method was more effective than conventional method. Then, we also leaded the correlate to cross term Hue, Value and Chroma. We analyzed with variance to know the relation between cross term each attribute. We modified the color difference and applied it to gamut compression.
The international standard sRGB has been established as the default RGB color space for multimedia, in which 'reference image display system characteristics' are specified. That is, a display device is required to have characteristics close to these characteristics in order to properly display color image data that is in conformity with sRGB. For this reason, the sRGB specification for front projectors has been defined. Our newly developed projectors achieve less than one tenth of the color difference for the sRGB specification. Today as more and more people use the Internet as a source of information and computer-aided visual presentations have become a key tool, accurate and reliable color reproduction is essential for everyone. With sRGB compliant projectors we can reproduce identical colors, ensuring that images shown on other sRGB compliant devices such as CRT display monitors remain the same.
This paper presents a new pixel slide method using optical deices for digital still cameras with a single-CCD to achieve high resolution. Authors have developed a new pixel- slide method using a double-refraction plate, a liquid crystal plate and a polarization filter, which takes advantage of the fact that a double-refraction plate has different indexes of refraction depending on the polarization direction. In addition, they have developed a ne color interpolation method to create a highly precise image form two images shifted by 1/2 pixel. The interpolation is conducted utilizing the color correlation. When a VGA- compatible CCD was employed in a digital still camera, resolution of 800 lines was obtained by using the proposed method. When an SXGA-compatible CCD was used, resolution of 1600 lines was obtained.
The authors have developed a new color conversion system that can contribute to the improvement of imperfect color reproduction in various types of displays, especially those of non-CRT displays such as TFT-LCD monitors. This paper describes the new color conversion system and touches on modeling of the TFT-LCD monitors. The new system is a system that uses a new matrix calculation that we have developed. Owing to its ease in hardware application, this color conversion system allows support of motion picture display and real time processing. In addition, it enables realization of desired color conversion characteristics and it also facilitates realization of use to two and more types of color conversion characteristics by selection. The authors have also developed color conversion simulation software based upon high-accurate modeling of the TFT-LCD monitors which can be applied to a practical TFT-LCD monitor to set the parameters of new color conversion system to an optimal condition.
A highly accurate multispectral camera and the application software have been developed as a practical system to capture digital images of the artworks stored in galleries and museums. Instead of recording color data in the conventional three RGB primary colors, the newly developed camera and the software carry out a pixel-wise estimation of spectral reflectance, the color data specific to the object, to enable the practical multispectral imaging. In order to realize the accurate multispectral imaging, the dynamic range of the camera is set to 14 bits or over and the output bits to 14 bits so as to allow capturing even when the difference in light quantity between the each channel is large. Further, a small-size rotary color filter was simultaneously developed to keep the camera to a practical size. We have developed software capable of selecting the optimum combination of color filters available in the market. Using this software, n types of color filter can be selected from m types of color filter giving a minimum Euclidean distance or minimum color difference in CIELAB color space between actual and estimated spectral reflectance as to 147 types of oil paint samples.
Color signal outputs form digital cameras can be calculated form spectral distribution of an illumination, spectral reflectance of a shooting object, and spectral responsivity of a camera. The methods of measuring spectral distribution of illuminations and spectral reflectance of objects have been established unambiguously, and their characteristics are available from various databases. However, no accurate methods have been clearly defined regarding the measurement of the spectral responsivity characteristics of digital cameras. For objective assessment of the performance of digital cameras which capture color images and output corresponding color information in red-green-blue digital image data, proposed methods incorporate measurements of characteristics for spectral responsivity and related items. In this paper, by adopting compensation of tone characteristics for each pixel, the authors develop yet another new method of measurements to overcome some possible defects in the previously proposed methods. The paper describes an arrangement of equipment, definition of test chart and raw data handling together with some worked examples. The newly developed method has made it possible to measure the spectral responsivity characteristics of digital cameras accurately.
The authors have newly developed measuring methods to assess and characterize color reproduction of digital still cameras and digital video cameras which capture color images and output corresponding color information in red, green, blue digital image data, the proposed new methods incorporate spectral responsivity characteristics measurements and other characteristics measurements. They are made possible by using newly developed test charts with a dark box and a spectral light source. The proposed set up for the measurements is specially effective to eliminate the influence of automatic functions commonly equipped in digital cameras for low-end consumer use. In this paper, arrangement of measurement equipment, definition of test charts, and raw data handling are described together with worked examples.